lecture #1 introduction to python - cypress collegestudents.cypresscollege.edu/cis247/lc01.pdf ·...

Python Programming – Penniel P. Wu, PhD. 1

Lecture #1 Introduction to Python

Introduction Python is a high-level general-purpose programming language, which means it is a language

designed to be used for writing software in a wide variety of application domains. It is an

object-oriented language, and is described by the 2017 IEEE Spectrum as an easy-to-use

programming language. In the field of cybersecurity, Python has earned a top position and

shows a tendency to quickly outperform other languages. Microsoft has included Python in its

Visual Studio, known as the Microsoft Python extension.

Python, in a nutshell, is a highly modularized language, which means it supports a large

number of standard libraries. Each of the modules is specially developed to support a different

programming task such as connecting to web servers, searching text with regular expressions,

reading and modifying files, system administration, and cybersecurity.

Python is a free, open source language maintained by the Python Software Foundation. Its

packages and source codes are available for download the at http://www.python.org

website. It is “free” in following two senses: cost and freedom.

• Cost: It does not cost anything to download or use Python, or to include it in your

application.

• Freedom: Python can also be freely modified and re-distributed, because while the

language is copyrighted it’s available under an open source license.

The latest generation of Python is Python 3. This lecture and all its sample codes are designed

based on Python 3.

Getting Python To a newbie, the learning journey starts with downloading and installing the Python

interpreter which is a program that reads Python codes and converts the Python codes to

machine codes.

Linux users probably do not need to go through the installation process, because most Linux

distributions come with Python pre-installed. Some Linux distributions provide Python 2, but

are readily for upgrading to Python 3. Mac OS X 10.8 comes with Python 2.7 pre-installed,

while Microsoft Windows operating systems do not have Python pre-installed. With that being

said, some Linux and Mac OS users might have to upgrade from Python 2.7 to Python 3. A

later section will provide some guidelines for Linux users.

Although Mac OS is not a supported platform for this course, students who choose to use Mac

OS can visit the https://docs.python.org/3/using/mac.html site for details about

installation and upgrading of Python.

Microsoft Windows users can download the Python package from many sources including:

• Python.org (http://python.org/download/). As of February 2018, the latest stable

release is 3.6.4 which was released on December 19, 2017. The file name is python-

3.6.4.exe for Microsoft Windows users. By the way, this is the primary source.

• ActivePython (http://www.activestate.com/activepython/downloads).

Python source codes Python intepreter Operating system


• Portable Python (http://www.portablepython.com/). This is a Python package

preconfigured to run directly from any USB storage device, enabling you to have, at any

time, a portable programming environment.

For Windows users, the instructor recommends students to install the Python package in a

USB drive for the sake of portability. For Linux users, the instructor suggests using a “Live

USB” version of Linux (e.g. such as Ubuntu). This course, however, does not suggest students

to use Mac OS.

Launch the

python

interpreter

An interpreter of a programming language is a program that reads and converts a sequence of

instructions in a script (the source codes) into machine codes for the computer to execute the

instructions on the fly. One major difference between Python and C, C++, Java, and C# is that

Python does not use “compiler”. A compiler is a program designed to read and convert the

source code into machine language to produce an individually executable program (such as

those of “.ext”). Python relies on the interpreter to effectively read and convert the source code

while a Python program is called for execution. In other words, a Python script is the program.

Python C, C++, Java, and C#

On the C, C++, Java, and C# side, once compiled, the source code is no longer needed. On the

Python side, the source code (script) is the only file needed to be called for execution.

Another benefit of using interpreter (instead of compiler) is that individual statement (typically

is only one single line) can be interpreted to produce immediate result, without the need of

compilation. During the first few lectures, the lecture notes will guide students through how to

use the Python interpreter to execute individual Python statements before organizing them as a

Python script.

The Python interpreter is a console application, which means it only runs in a command-line

interface (CLI) environment such as the “Command Prompt” of a Windows operating systems

or a terminal emulator of the Linux operating system, as shown below.

Windows Command Prompt Terminal emulator

The prompt (or shell prompt) is defaulted to display the home drive (e.g. “C:” of Microsoft

Windows or “/” of Linux) and the home directory (the directory the user is defaulted to use by

the system settings). The following is a sample prompt, in which “C” is the drive name, and

“C:\Users\D0213657” is the home directory, while “~” home directory of Linux. The greater

than sign (>) is the symbol of prompt for Windows operating system, while the dollar sign ($)

or pound sign (#) is the shell prompt for Linux. In a nutshell, the dollar sign ($) is for regular

Linux user, while the pound (#) sign is for the superuser (such as “root”).

Microsoft Windows Linux C:\Users\D02132657> [liveuser@localhost ~]$

Source

Code Interpreter

Output

Source Code

Compiler Executable

Output Executable


By typing cd \ (or cd / in Linux) and press [Enter] in the prompt, the “presently working

directory” changes to the root (\) directory which is typically represented by a letter (such as

“C”) in the Windows OS and a “/” in Linux, as illustrated below.

Microsoft Windows Linux C:\Users\D02132657>cd \

C:\>

[liveuser@localhost ~]$ cd /

[liveuser@localhost /]$

As stated previously, most Linux distributions come with Python preinstalled and pre-

configured. Ubuntu, for example, is one of the most popular distributions of Linux. Python

3.6 is installed on all stable release of Ubuntu 14.04 or later. In a Linux machine, the Python

interpreter is usually installed in the “/usr/local/bin/” directory of the file system. In a

Python 3 pre-installed Linux environment, Linux users can simply type python3 and press

[Enter] in the shell prompt to launch Python. Once launched, the Python shell (“>>>”), as

shown below, will appear.

[liveuser@localhost ~]$ python3

Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep 1 2017, 02:16:59) [GCC

7.1.1 20170802 (Ubuntu 7.1.1-7)] on Linux

Type "help", "copyright", "credits" or "license" for more

information.

>>>

Interestingly, users of Microsoft Windows operating systems need to add the path of the

Python directory in the “PATH” environment variable in order for the operating systems to be

able to locate the Python interpreter. The “PATH” variable is an operating systems variable

that specifies a set of directories where executable programs are located. By default, the path

to Python interpreter such as “C:\Python36\” is not added to the “PATH” environment

variable. The following demonstrates how to manually configure the path settings (assuming

the path is “C:\Python36\”). By the way, environment variables in Windows are denoted with

moduli surrounding the name; therefore, the value of the “PATH” variable is denoted by

“%PATH%”.

C:\>PATH = %PATH%;C:\Python36;

The following is another way to set the path. It uses the DOS “set” command.

C:\>set path=%path%;C:\Python36;

After the path setting, Microsoft Windows user can open the Command Prompt, and then type

python.exe (or simply python) and press [Enter] to launch the Python interpreter. If the

path setting went successfully, the following (or similar) message will appear.

C:\>Users\D00182312>python

Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep 1 2017, 02:16:59) [MSC

v.1900 32 bit (Intel)] on win32

Type "help", "copyright", "credits" or "license" for more

information.

>>>

It is necessary to note that “>>>” is the Python prompt. It is the intermediary between the

Python programmer and the Python interpreter. The prompt takes a Python statement (which

consists of Python commands, arguments, expressions, or a combination of them), interprets


the Python statement, and then produce the output. The following is a sample Python

statement.

>>> print("Hello World!")

The given Python statement will be temporarily store in the memory (such as DRAMs). The

programmer must press the [Enter] key to notify the shell prompt to pass the given Python

statement to the Python interpreter for execution. The following figure illustrates how Python

complies with the “IPO” model, where “I” is short for “input”, “P” for “processing”, and “O”

for “output”.

There is a tool, known as “IDLE” (stands for Integrated DeveLopment Environment), which is

a simple IDE (integrated development environment) for Python. For Windows OS users, the

tool is bundled with the Python package, and is available at the “Lib\idlelib” subdirectory of

Python’s directory (such as “X:\python36\ Lib\idlelib”, in which “X” is the drive name) and

the file name is “idle.bat”. The following is a screen shot of Windows version of IDLE.

Ubuntu users need to install the “IDLE” program by issuing the following command.

$ sudo apt-get install idle3

The following is the command for launching “IDLE” in a Linux shell prompt.

$ idle

Throughout this course, students are not required to use “IDLE”. Executing Python scripts

does not require the use of IDLE. It is not necessary to install IDLE if it is not available.

Python

expressions and

statement

In terms of programming, a statement is an instruction for the computer program to perform

an action. In Python, a statement can be an individual instruction given to the interpreter to

produce a value as result. A Python statement can also be a syntactic unit of a program when a

sequence of statements is organized into a Python script. A Python script is a program written

consists of a sequence of one or more statements.

A statement may have internal components. A Python statement can include a combination of

keywords, commands, functions, and expressions. The following is a sample statement that

uses the “print” function to display the result of an expression. By the way, pressing the

[Enter] key means to instruct the Python interpreter to execute the Python statement, according

to the “Store-and-Forward” mode.

>>> print(5<3)

An expression is a combination of explicit values, constants, variables, operators, and/or

functions to indicate a state or a condition. In the above statement, (5<3) is an expression

which will be evaluated to be false.

Python Prompt Python Intepreter

input

output


Statements are interpreted according to rules defined by the programming language to

compute and/or produce another value. Although later lectures will discuss variables and

operators in details, this section will use simple variables and operators to illustrates how the

Python prompt handles Python expressions as statements.

The following is a sample expression, x=21, which assigns 21 to a variable named x, and x is

the “identifier” of a variable the statement declares. By the way, the “=” is known as the

“assignment” operator. A later lecture will discuss about the concept of “operator” in detail.

>>> x=21

In terms of programming, a “string” literal must be enclosed by a pair quotes, either single or

double quotes. The following assigns two string “21” and ’37.4” to variables y and z. The

difference between the following two statements and the above is that 21 of the above

statement is a number (which indicates “units”), while “21” and ’37.4’ in the following are

“texts” not “numbers”.

>>> y = "21"

>>> z = '37.4'

Interestingly, the data type of the variable x is specified by the value it holds or the value it is

assigned. In the following example, 21 is an integer, the data type of x is automatically

converted to integer by Python interpreter.

>>> x=21

Unlike C++, C#, or Java, Python does not require programmers to specify the data type of a

variable with a “data type” keyword (such as int, float, char, string, bool, etc.) as prefix. The

following table compares Python’s variable declaration with other languages.

C++ Java JavaScript PHP Python int x = 21; int x = 21; var x = 21 $x = 21; >>> x = 21

After assigning a value to a variable, the Python prompt can display the value held by the

variable by simply typing the identifier of the variable. The following is the expression that

asks the prompt to return the value held by the variable x. With that being said, a value held by

a variable can be displayed by typing the identifier of the variable in Python.

>>> x

21

The following is another expression, x = 12**2, which assigns the value 122 (or 12 to the 2nd

power) to a variable x.

>>> x = 12**2

The above statement uses two operators:

• the assignment operator (=) which assigns a value to x and;

• the exponentiation operator (**) to raise 12 to its second power.

The expression, a**n, means “a raised to nth power” (or an). By the way, 122 is 144;

therefore, the value of x is 144.

In mathematics, there exists the fact that √𝑎𝑛

= 𝑎1/𝑛; therefore, √3 = 31/2 = 30.5. In Python,

the squared root of 3 can be calculated by the following statement.

>>> 3**0.5


1.7320508075688772

Since 0.5 = 1

2, the following return the same result.

>>> 3**(1/2)

1.7320508075688772

The following expression, x/2, which means “return the value of x divided by 2”. Since the

previous statement already assigned a value to x, this expression will return the calculation

result of x/2 on the screen.

>>> x/2

72.0

The following assigns 4.35 to a variable y.

>>> y = 4.35

The following asks the prompt to return the value of y times 2. Interestingly, the precision of

calculation result varies from one operating systems (OS) to another. This is not a bug or error

of the operation system. It is a result of the fact that most decimal fractions cannot be

represented exactly as a float. Floating-point numbers are represented in computer hardware as

binary fractions (base 2), yet, they must be converted to decimal fractions (base 10).

Unfortunately, the result of conversion is usually a close approximate, not the exact value.

Windows 7/8 Linux >>> y*2

8.7

>>> y*2

8.699999999999993

Users can treat the Python prompt as an electronic calculator. The following example uses the

Python interpreter as a simple calculator to perform an arithmetic expression.

>>> 5.231 * 6.172 * 29

936.28622799999994

The following calculates the sum of 2 + 6, which is 8.

>>> 2 + 6

8

Python prompt can handle calculation of complex numbers. A “complex number” is a

number that can be expressed in the form a + bi, where a and b are real numbers and i is the

imaginary unit, that satisfies the equation x2 = −1, that is, i2 = −1.

>>> (3 + 1j) * (3 - 1j)

(10+0j)

The following returns the calculation results of 22 divided by 7. It is necessary to note that,

during the calculation, Python 3 will automatically “cast” the integers, 22 and 7, to floating-

point values, 22.0 and 7.0. The term “cast” means “temporarily convert from one data type to

another”. By the way, in some operating systems, the output could be 3.1428571428571428.

>>> 22 / 7

3.142857142857143

Interestingly, Python 2 does not automatically “cast” data types. Therefore, a Python 2

interpreter will return 3 as result of 22/7 instead of 3.142857142857143. Such as result was


caused by “data type”. Python 2 returns the calculation return based on the data types. Both 22

and 7 are integers; therefore, Python 2 only returns the integer part of result of 22/7.

When a user assigns a value to a variable, the Python prompt immediately works with the

operating system to allocate a free memory space (typically DRAMs) to store the value. The

identifier of the variable is used to represent the memory block. In other words, Python stores

the value of a variable in computer’s memory (or DRAMs). Therefore, the value of a given

variable can be continuously updated. Yet, only the final value is returned to prompt. In the

following example, the variable x is assigned to hold 4. Then, it is instructed to clear 4 and

hold a new value 2.1. A newer value 3.0 is assigned to x, therefore, the final value is 3.0.

>>> x=4

>>> x=2.1

>>> x=3.0

>>> x

3.0

In the following, the variable fullname is assigned a string “Taylor Swift”.

>>> fullname = "Taylor Swift"

By typing the identifier, fullname, Python prompt returns the value stored in the “fullname”

variable.

>>> fullname

'Taylor Swift'

In the following example, the “multiplication” operator (*) can return the same string literal

twice.

>>> course = "Python Programming"

>>> course*2

'Python ProgrammingPython Programming'

The following are sample expressions that compare strings alphabetically using comparison

operators. A later lecture will discuss comparison operators in detail. By the way, the word

“schools” is listed after the word “school”; therefore, the index of “school” is less than

“schools” because the index of 14th word is less than 17th word.

>>> "apple" < "orang"

True

>>> "tree" == "Tree"

False

>>> "schools" > "school"

True

>>> "Home" != "Home"

False

Syntax for

writing Python

statements

As stated previously, in terms of programming, a statement is the instruction written by

elements of a programming language to perform some action. A Python program is formed by

a sequence of one or more statements. Each statement either a single line of code or or a block

of code.

In the following example, the instructor demonstrates how to write a statement

print('Hello World') in the prompt as a single-line code. This Python statement uses the

print() function to request the Python interpreter to display a string literal on screen. The

Python core provide many “built-in functions” created by the programmers who contributed

to develop the language core. A later lecture will discuss about “functions” in detail.


>>> print('Hello World')

Hello World

>>>

The Python interpreter reads the print('Hello World') statement, and follows its

instruction to display a string literal on the screen. By the way, the print() function is created to

display a value on the default output device (typically the screen). It can output either a literal

string of characters or the value of a variable.

A Python statement can be structural, such as the if..else structure. The following is a

structural statement that use the if..else structure to evaluate an expression (8 > 5, which is a

mathematical condition), and then print the result based on the result of evaluation. A later

lecture will discuss about the if structure in detail.

if (8 > 5):

print("Correct!")

else:

print("Incorrect!")

In Python, a “user-defined function” is a block of organized, reusable codes that is created by

programmer to perform a specific task. In the following example, the identifier of the function

is “findMax”. The first line of statement is max = list[0] which is a single-line code. There

is a for loop for iterations. The entire for loop can be considered as one statement. However,

the for loop contains an if structure. The entire if structure is a one single statement. That’s

being said that the for statement is a nested statement because it is a single statement that

contains one or more statements. A later lecture will discuss about the for loop in detail.

def findMax(list):

max = list[0]

for a in list:

if a > max:

max = a

return max

The following is a list of statements. Each statement is an individual one that performs a

unique action. Although each of them is a single-one statement, they are arranged in sequence

to collaboratively perform a specific task--they calculate and display the total dollar amount

with a dollar sign ($).

>>> unit_price = 5.75

>>> qty = 12

>>> print("$", unit_price * qty)

$ 69.0

It is necessary to note that Python 3 allows programmers to use the print() function to

enclose two or more values on a single line with commas (,) as separator, as shown below. The

print() function will concatenate these enclosed values into a single string, separated by

spaces. The term “concatenate” means “to combine”.

>>> print("This is", "a sample", "value", 3*15)

This is a sample value 45

Interestingly, without the presence of comma, the print() function automatically concatenate

two adjacent strings without a space in between, such as “Python” and “3”, as demonstrated

below. Although, there is a blank space between the two adjacent strings, ("Python" "3"),

this blank space is used to separate the two string literals, “Python” and “3”. This blank space

is not for concatenation between the two adjacent values.


>>> print("Python" "3")

Python3

The following is a list of statements that uses the int() function to convert a numerical value

from floating-point to integer. The int() function is Python built-in function that converts a

string or a non-numeric variable to integer. If the numerical value contains fractional part

(3.14), the fraction part will be ignored (3).

>>> x = 3.14

>>> int(x)

3

The following convert a string type to float type using the float() function. The float()

function returns floating-point number from a number or a string. It is necessary to note that,

when a value is enclosed by quotes (either single or double quote), the value is a string type. A

numeric value is a value that consists of only digits and is not enclosed by quotes. In the

following example, both '0.5382' and "0.5382" are string, but 0.5382 is a number. By the

way, in some operating system, the output of print(float(y)) could be

0.53820000000001.

>>> y = "0.5382"

>>> y

'0.5382'

>>> print(float(y))

0.5382

The following is another example of “multiline” statements typed directly into the Python

prompt. The first line (x = 5) is not part of the multiline statement; it is a single-line

statement that assigns 5 to the variable x.

>>> x = 5

>>> if x > 3:

... print("Correct!")

...

Correct!

The if statement consists of two lines arranged in two layers for hierarchy. The first layer, if

x > 3:, and the second layer, print("Correct!"), must be distinguished by “indentation”.

The term “indentation” refers to the use of spaces and tabs at the start of a line of code or text

to indicate the layer the line belongs to. It is necessary to note that the second line and beyond

of an “if” statement must be indented. Likewise, the second line and beyond of an “else”

statement must be indented. As a principle, after the colon (:), Python interpreter expects the

next line to be indented. However, Python does not specify the number of blank space per

indent; therefore, the instructor uses 1 blank space per indent.

Interestingly, Python prompt displays three dots “...” instead of the standard Python prompt

“>>>” to imply the “continuation” of statement. In a sense, it indicates the statement is not

complete. In the following example, the if statement contains 4 lines.

>>> x = 15

>>> if (x/3 > 6):


... else:

... print("Wrong!")

...

Wrong!


The following is another example of multiline statement, in which the for loop has two lines.

The multiline statement starts at the keyword “for”. The first line (y = (0, 1, 2, 3, 4,

5)) is a single-line statement that defines an integer tuple named “y”. A Python “tuple” is a

collection of value similar to an array of C++, C#, or Java. A later lecture will discuss “tuple”

in detail.

>>> y = (0, 1, 2, 3, 4, 5)

>>> for n in y:

... print(n)

...

0

1

2

3

4

5

In the following example, the instructor adds an if statement within the for statement;

therefore, the multiline statement contains 5 lines.

>>> y = (0, 1, 2, 3, 4, 5)

>>> for n in y:

... if n == 2:

... print(n*n)

... else:

... print(n)

...

0

1

4

3

4

5

Similar to C++, C#, and Java, a semicolon (;) is a wildcard character that means “the end of a

line” in Python. The following single-line statement is equivalent to a multiline statement.

Multiline statement Single-line statement >>> w = 6; x = 5; y = 3; z = 7; >>> w = 6

>>> x = 5

>>> y = 3

>>> z = 7

Another way to make a statement extend over multiple lines is to use the line continuation

character (\). The following demonstrates how to break a lone single-line statement to three

smaller lines.

Single-line statement Multiline statement >>> 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9

45

>>> 1 + 2 + 3 + 4 \

... + 5 + 6 \

... + 7 + 8 + 9

45

The following is another example. The line continuation character (\) forces Python interpreter

to treat the multiline statement as a single-line statement. By the way, this example also uses

the “+” sign as the concatenation operator to “combine” all strings into one single string.

>>> "An" + " apple a day " + \

... "keeps doctors" + " " + \


... "away."

'An apple a day keeps doctors away.'

Interestingly, a pair of parentheses, brackets, or braces can also implicitly force Python

interpreter to treat the content enclosed by them as a single-line statement. The following

demonstrates how to use parentheses to enclose a multiline statement.

>>> (1 + 2 + 3 +

... 4 + 5 + 6 +

... 7 + 8 + 9)

45

The brackets can also enclose a multiline statement, yet, it could function differently. Brackets

in Python are commonly used to create a “list”. A Python “list” is a container that holds a

number of other objects, in a given order. A later lecture will discuss it in detail.

>>> [1 + 2 + 3 +

... 4 + 5 + 6 +

... 7 + 8 + 9]

[45]

While square brackets create lists, curly braces create dictionaries or sets in Python. A Python

“dictionary” is a collect of value with index. In a dictionary, each value has an “index” that

represents the value. In python, the word is called a “key”, and the value is its definition.

>>> months = {'01':'January', '02':'February', '03':'March', \

... '04':'April', '05':'May', '06':'June', \

... '07':'July', '08':'August', '09':'September', \

... '10':'October', '11':'November', '12':'December'}

>>> print(months)

{'11': 'November', '10': 'October', '12': 'December', '02':

'February', '03': 'March', '01': 'January', '06': 'June', '07':

'July', '04': 'April', '05': 'May', '08': 'August', '09':

'September'}

The Python prompt provides the input() function to: (a) display a message and pauses for

user inputs, (b) read a line entered by the user from the keyboard through the Python prompt,

(c) convert the input to a string, and (d) pass the input to the designed destination. In the

following example, the destination is a variable named “fullname”. By the way, it pauses for

user inputs.

>>> fullname = input('Enter your full name: ')

Enter your full name:

User can then type a value as inputs (e.g. “Taylor Swift”). The given entry will be stored in the

variable named “fullname” for later use.

Enter your full name: Taylor Swift

The following uses the print() function to retrieve the value stored in the “fullname” variable

and concatenate it with another string “Hello”.

>>> print('Hello', fullname)

Hello, Taylor Swift

In the following example, the print() function automatically concatenates all the strings. The

instructor purposely places every individual string in a separated line.

>>> print("<!Doctype html>"


... "<html><body>"

... "<h2>Welcome to CIS247!</h2>"

... "</body></html>")

<!Doctype html><html><body><h2>Welcome to

CIS247!</h2></body></html>

In the following example, the instructor uses commas to add a blank space between every two

lines.

>>> print("<!Doctype html>",

... "<html><body>",

... "<h2>Welcome to CIS247!</h2>",

... "</body></html>")

<!Doctype html> <html><body> <h2>Welcome to CIS247!</h2>

</body></html>

In the following example, the instructor uses the newline (“\n”), which is one of the escape

sequences, to insert a newline in the text at this point.

>>> print("<!Doctype html>\n"

... "<html><body>\n"

... "<h2>Welcome to CIS247!</h2>\n"

... "</body></html>\n")

<!Doctype html>

<html><body>

<h2>Welcome to CIS247!</h2>

</body></html>

Python

Scripting

Scripting is the arrangement of series of statements with logical flow and sequence in a text

file. The text file is known as a “Python script”, which will remain being a text file throughout

its life span. A generic text editor like Notepad of Windows operating system or the “gedit” of

a Linux operating system is functionally sufficient to create and edit the script.

As stated previously, the Python prompt is designed to read only one statement at time, store

the statement in memory, and then execute the statement only if the [Enter] key is pressed by

the programmer. However, as a matter of fact, the Python interpreter can read a batch of

statements from a “Python script”, and then execute these statements one by one. The

following demonstrates how to organize a list of Python statements into a “Python script”

named “test.py”. By the way, “Python script” must use “.py” as file extension.

Statements in the Python prompt Statements organized as a Python script >>> i = 5

>>> print(i)

5

>>> i = i + 1

>>> print(i)

6

>>> i = i - 3

>>> print(i)

3

It is necessary to note that the content of the “test.py” file does not contain the Python prompt

(>>>). The following is the content.

i = 5

print(i)

i = i + 1

print(i)

i = i - 3


print(i)

The following demonstrates how to call the Python interpreter in a Microsoft Windows

Command Prompt and a Linux terminal to execute the “test.py” script without launching the

Python prompt (assuming “test.py” is saved in the “C:\cis247” directory (or “~/cis247” of

Linux) and Python package is successfully installed).

Windows OS Linux C:\User\D02132657>cd \

C:\>cd cis247

C:\>cis247\python test.py

$ cd ~

$ cd cis247

$ python test.pty

In the above Python script, there are three statements that use the print() function to display

the value of the variable i.

print(i)

The value of i was originally 5, later changed to 6 (because i=i+1 means “add 1 to i”), and

eventually changed to 3 (because i=i-3 means “subtract 3 from i”), the output is:

Windows OS Linux C:\>cis247\python test.py

5

6

3

$ python test.pty

5

6

3

The following is another sample script. It starts with assigning values to x and y variables,

continue with constructing an if statement to evaluate an expression (x > y), and displaying

the message based on the result of evaluation. By the way, the instructor purposely

demonstrates that the input() function can enclose a string with either double or single

quotes.

x = input("Enter the value of x: ")

y = input('Enter the value of x: ')

if (x > y):

print(x, "is greater than", y)

x = x - 1

else:

print(x, "is less than or equal to", y)

Many Linux distributions require Python scripts to add the following line, known as the

“shebang”, at the beginning of Python scripts. A “shebang” line defines where the Python

interpreter physically resides in a Linux file system. It is necessary to note that “shebang” of

two Linux operating systems might point to two different paths, although it typically looks

similar to the following.

#!/usr/bin/python3

The following is the Linux version of the above code.

#!/usr/bin/python3

x = input("Enter the value of x: ")

y = input('Enter the value of x: ')

if (x > y):


x = x - 1


else:


The “shebang” line is not required by Python scripts for Windows operation systems. Whether

or not to specify the shebang for Windows-based Python scripting is the programmer’s

decision. The following is a sample “shebang” for Windows-based Python scripts.

#!C:\Python36\python.exe

The following is a sample Shebang for Portable Python 3.2.5.1 users (assuming “F” is the

drive name of USB drive).

#!F:\Portable Python 3.2.5.1\App\python.exe

Python scripting is typically used to develop applications to solve problems. For example, the

formula to converts a temperature degree in Fahrenheit to Celsius is: C = (F-32) × 5

9, where F

is the degree in Fahrenheit and C is the degree in Celsius. The following is a sample Python

script that uses: (a) the input() function to take a string value (which is the degree in ) from the

user, (b) the float() function to convert the string value to a float-point value, (c) perform an

arithmetical calculation to obtain the degree in Celsius, and (d) display the degree in Celsius

with the str() function to convert the numerical value to a string.

F = float(input("Enter the degree in Fahrenheit: "))

C = (F-32)*(5/9)

print(str(C))

It is necessary to note that any input entered through the keyboard is treated as a string by

default. A string value cannot go through an arithmetical calculation; therefore, it is necessary

to convert a string value to a numerical value before performing the calculation. Interestingly,

the print() function only print a string literal, thus, the str() function is needed.

What is a

module in

Python?

A Python module is a Python source file that provides definition of functions, variables, or

classes. Similar to a Python script, Python modules are reusable Python codes created by

programmers and then share the modules with the Python coding community as libraries.

Python comes with many built-in modules that are organized into packages. The following

statements start with loading a built-in module named “sys” using the “import” keyword. The

“sys” module provides access to some variables used or maintained by the interpreter and to

functions that interact strongly with the interpreter. The print(sys.version) statement

uses the “version” variable provided by the “sys” module to display the version of Python by

accessing the version variable of the “sys” module.

>>> import sys

>>> print(sys.version)

3.25 (default, May 15, 2013, 23:06:03) [MSC v.1500 32 bit

(Intel)]

The “os” module provides tools to use operating system dependent functionality. The

“os.name” property, for example returns the name of the operating system the os module is

currently running on. Yet, it only provides three possible outcomes: posix (Linux), nt

(Windows), and java (Android).

>>> import os

>>> print(os.name)

nt

Python modules and Python scripts are similar in some respects. Students frequently get

confused about them due to the following commonalities.


• file name of both modules and scripty must end with the “.py” extension;

• both scripts and modules can be packed into a package and share with the Python

community as a library (a later section will discuss about the concept of “Python library”

in detail);

• programmers can freely create modules just like how they create scripts; and

• they are files consisting of Python codes.

A later lecture will discuss how to create a custom-made module. The following is a simple

module named “exp”, its file name is “exp.py”. This module contains only one function

named “exp()” which requires two parameters, x and y, to perform an exponentiation operation

with the exponentiation operator (**). By the way, in Python, a function block begins with the

keyword “def”. A later lecture will discuss about how to create user-defined functions in

detail.

# exp module

def exp(x, y):

print(x**y)

Definitions from a module can be imported into a Python script or other modules with the use

of “import” keyword. The following demonstrates how to load this module into memory.

>>> import exp

The following illustrates how to call the exp() function of the “exp” module. It also passes two

integers, 2 and 3, to the exp() function for a 2**3 operation.

>>> exp.exp(2,3)

8

The following is an example that convert one of the previous Python script to a Python module

named “comp”. The file name of this module is “comp.py”.

# comp module

def compare(x, y):

if (x > y):


x = x - 1

else:


Programmers who wish to use this module must import it with the “import” keyword in the

Python prompt, as shown below.

>>> import comp

The following demonstrates how to call the compare() function of the “comp” module. It also

passes two integers as parameters of the compare() function.

>>> comp.compare(5,3)

5 is greater than 3

A package is a collection of modules in directories that give a package hierarchy. A later

lecture will discuss about how to organize multiple modules into a package. The following

illustrates the structure of a simple one-file Python package named “project”.

project/

exp.py

comp.py


What is a

Python library?

A “Python library” is a collection of useful Python codes, modules, and/or packages, to

provide a specialized functionality such as game engine or scientific calculations. Most of

Python libraries are explicitly designed to provide or enhance the functionality of the standard

Python software provided by the Python Software Foundation.

Python software frequently comes with third-party libraries. The “ctypes” library, for

example, is a third-party library for Python. The following demonstrates how to load the

“ctypes” library with the “import” keyword.

>>> import ctypes

The “tkinter” module (also known as “Tk interface”) is a library for Python to create GUI

(graphical user interface) applications, similar to a Windows Form application. Although it

was originally designed for the Unix/Linux platform, “tkinter” now can work in a Windows

operating system. Ironically, the “tkinter” module was originally named “Tkinter” with a

capital “T”, and has been renamed to “tkinter” with a lower-case “t” in Python 3. A later

lecture will discuss about this module in details. The following is a Python script created by

the instructor using the “tkinter” module. It simply produces a “message box” for students to

use in throughout this course. The code is also available in Appendix A.

#File name: MessageBox.py

import tkinter

from tkinter import *

def Show(str):

root = Tk()

root.title('Message Box')

Label(root, justify=LEFT, text = str).grid()

root.mainloop()

The following is a Python script named “1.py” that illustrates how to: (a) create a string

variable name “s” with a null as its initial value; (b) use a for loop to concatenate 0 to 9 to the

“s” variable; (c) convert integers (0 to 9) to strings with the str() function; (d) use the “import”

keyword to insert source code of the “MessageBox.py” file and use it as a custom-made

module; and (e) call the “Show()” function of the “MessageBox” module to display the result

in a GUI application.

s = ""

for i in range(10):

s += str(i) + "\n"

import MessageBox

MessageBox.Show(s)

In the above example, the “MessageBox.py” includes a user-defined function named “show()”

for programmers to call to display a pop-up window as shown by the figure. Interestingly, the

following code can be added to any Python script to display the output in a pop-up window

similar to the above figure, without calling the “Show()” function.

str = ""


root = Tk()


Label(root, justify=LEFT, text = s).grid(padx=10, pady=10)


root.mainloop()

In this course, the instructor also creates a “InputBox.py” module which can take user input

from a GUI application. The source code is available in Appendix A. The following is a

sample Python script that demonstrates how to use the “InputBox.py” module. It also uses the

“MessageBox.py” module to display the output in another GUI application.

import InputBox

InputBox.ShowDialog("Enter the 1st Fahrenheit value:")

f = InputBox.GetInput()

c1 = (float(f) - 32) * (5/9)

InputBox.ShowDialog("Enter the 2nd numberFahrenheit value:")


c2 = (float(f) - 32) * (5/9)

import MessageBox

MessageBox.Show(str(c1) + "\n" + str(c2))

The above code starts with “importing” the code of “InputBox.py” module, continues with

calling the ShowDialog() method to display a dialog box for user input, and then calling the

GetInput() method to retrieve the user input. Eventually the user input is assigned to a string

variable “f”. With the use of float() function, the value of “f” is converted to float type for

calculation based on a formula: C = (F-32)×5/9. The same procedure repeats twice. Two float

variables, “c1” and “c2” stores the calculation results.

A sample output looks:

and

Solving a

display issue

In programming, outputs of a data to the screen or a message box (as the one created by the

instructor) are treated as string texts regardless to their data type. In the following, the variable

x is assigned a value 21, which is an integer; therefore, the data type of x is int. In order to

store the value of x in another variable s of string type, the instructor uses the str() function

to convert x from int to string.

>>> x=21

>>> s = str(x) + "\n"

In Python programmers can convert between types you simply use the type name as a

function. The following are some commonly used converters.

• int(x): Converts x to an integer. base specifies the base if x is a string.

• float(x): Converts x to a floating-point number.

• str(x): Converts object x to a string representation.

• chr(x): Converts an integer to a character.

• unichr(x): Converts an integer to a Unicode character.

• ord(x): Converts a single character to its integer value.

Comment in

Python

In programming, a “comment” is an annotation, programmer's notes, or text-based

explanations placed in the source file for human reader to use as reference. Through the

course, the instructor will frequently add “comments” to demo Python scripts.


A single-line comment starts with the hash (#) symbol. Programmers can place only one single

line of text next to the hash symbol, as shown below. The comment, assign 5 to x, which

is placed next to the hash symbol is completely ignored by Python interpreter.

>>> x = 5 # assign 5 to x

The following is another example.

>>> s = "They said," # "An apple a day keeps doctors away"

>>> s

'They said,'

In a Python script, comments are annotated text added by programmers to describe, explain, or

remind the human reader how and why the program works. Comments are ignored by Python

interpreter. Multiline comments must be enclosed by a pair of triple quotes, either ''' or """.

Multiline comments are typically used in Python scripts. The following demonstrates how to

add multiline comments to the “test2.py” script using '''.

'''

File name: test2.py

Programmer: John Doe

Date: Jan 16, 2019

'''

x = 5

y = 3

The following uses """ to enclose multiple lines of comments.

""" compare the value of x and y

display the output based on

the result of comparison

"""

if (x > y):


x = x - 1

else:


Getting online

help

Python 3 comes with an online helper, the help utility, which is a built-in function designed to

print out the documentation of Python tools. Simply type help() and press [Enter] to launch

the online help utility. It is necessary to note that the prompt will change to “help>” which is

known as the “Help” prompt.

>>>help()

Welcome to Python 3.4! This is the online help utility.

......................

......................

help>

In the “Help” prompt, type print and press [Enter] to learn how to use the print function.

help> print

Help on built-in function print in module builtins:

print(…)

print(value, ..., sep='', end='\n', fill=sys.stdout)

...............


In the “Help” prompt, type quit and press [Enter] to quit the online help and return the

regular Python prompt.

help> quit

>>>

The following uses the help() function to provide information about the exp() function of the

math module.

>>> help(math.exp)

Help on built-in function exp in module math:

exp(…)

exp(x)

Return e raised to the power of x.

Special note for

Python 2

programmers

As stated previously, as of February 2018, there are currently two major versions of Python

used in the industry: Python 2 and Python 3. Although Python 2 is probably more popular and

commonly used by many programmers, this course is based on Python 3 for future

expandability. Additionally, there are many improvements being made to Python in version

3.0 to make the language cleaner and more consistent.

It is the instructor’s opinion that Python 3 is moderately different from Python 2. All the

language cores remain the same, except for some minor incompatibilities. An experience

Python 2 programmer can quickly migrate to Python 3 by learning the version differences. The

language is mostly the same; however, many details, especially how built-in objects like

dictionaries and strings work, have changed considerably, and a lot of deprecated features have

finally been removed. Also, the standard library has been reorganized in a few prominent

places. It is necessary to note that some of Python 2 scripts will not run under Python 3.

Lennart Regebro (2013) prepares a list of the differences between Python 2 and Python 3 and

provides sample codes to illustrates how to work around the differences between Python 2 and

Python 3. Although the list is incomplete, it is a good reference for experience Python 2

programmers. The list is available at http://python3porting.com/differences.html.

One important difference is the “print” statement. In Python 3.x, “print” is no long a

statement. It has been replaced by the print() function, as illustrated below.

2.x 3.x print "Welcome to CIS247!" print("Welcome to CIS247!")

The print() function does not support the “softspace” feature of the old print statement. For

example, in Python 2.x, output of the following statement is equivalent to print("A\nB\n")

of Python 3.

print "A\n", "B"

Interestingly, in Python 3.0, the following statement is equivalent to print("A\n B\n").

The print() function automatically adds a blank space between "A\n" and "B".

print("A\n", "B")

On the other hand, Python 3 has many improvements that can make the programming

smoother. For example, Python 3.0 changes the way it handles integer division (such as 3/5);

therefore, the division operation of two integers (such as 5/7) will returns a float value. Python

2.x adopts the convention similar to that of C++, C#, and Java, integer division is implemented

as “floor division”; therefore, the result of 1/2 is 0, not 0.5. The following table illustrates the

difference.


Python 2.x Python 3 >>> 1 / 2

0

>>> 1 / 2

0.5

By the way, the integer division operator (//) can be used to obtain the old behavior:

>>> 1 // 2

0

Another example is that Python 3 is relatively easier in reading a number. The code has been

simplified to the following: >>> x = input('Enter a value: ')

Enter a value:

Review

Questions

1. If the Python software is installed in C:\python39 directory, which of the following can

correctly add the "C:\python39" directory to Windows' "PATH" environment variable?

A. PATH = path(%PATH%, "C:\python39");

B. PATH = %PATH%, "C:\python39"

C. PATH = %PATH% + "C:\python39"

D. PATH = %PATH%;C:\python39;

2. Which is the Python prompt?

A. C:\python>

B. >>>

C. $

D. [root@localhost ~] #

3. Which correctly describes the following Python expression?

>>> x = "3"

A. It assigns an integer 3 to a variable x.

B. It forces the variable x to become integer type.

C. It assigns a string to a variable x.

D. It renames the variable "x" to "3".

4. In the Python prompt, what is the possible output of the following statement?

>>> 3 + 5

A. 3+5

B. '3+5'

C. 8

D. '8'

5. When using the Python prompt as an eletrical calculator, which of the followng can return

the square root of 7?

A. 7**(1/2)

B. 7**1/2

C. (7**1)/2

D. 7**2

6. In the Python prompt, the output of the following is __.

>>> x = 1


>>> y = 2

>>> x + y

A. 1

B. 1 + 2

C. x + y

D. 3

7. Which is the expected output of the following Python statement?

>>> print("Recycle" "the" "trash")

A. Recycle the trash

B. "Recycle the "trash"

C.Recyclethetrash

D. "Recycle" "the" "trash"

8. Which is the expected output of the following Python statements?

>>> i = 5

>>> i = i - 1

>>> i

A. 4

B. i

C. 'i'

D. 'i - 1'

9. Which can load a Python module named "Star2"?

A. >>> load Star2

B. >>> import Star2

C. >>> include Star2

D. >>> using Star2

10. Which is the expected output of the following Python statements?

>>> x = "She said," # "Hello world!"

>>> x

A. "She said, # Hello world!"

B. 'She said,'

C. She said, "Hello world!"

D. 'She said, Hello world!'


Lab #1 Introduction to Python

Preparation #1: (For Linux user, skip preparation #1 and #2. But read Appendix B)

1. Use a browser to go to https://www.python.org/downloads/ to download the latest version of Python.

As of the day this handout is written, it is version 3.6.4.

2. Click the downloaded .exe file (e.g. python-3.6.4.exe) to launch the installation wizard.

3. In the following screen, be sure to write the the directory path (e.g.

C:\users\user\AppData\Local\Programs\Python\Python36-32). Check the “Add Python 3.5 to

PATH” box, and then click “Install Now”.

4. Wait till the “Setup Progress” page pops up.

5. Wait till the installation completes, and then click Close.

Check this box

Write down the path


6. Use Windows Explore to verify that the “python36-32” directory is installed in the designated directory.

7. Open the Command Prompt, type python and press [Enter]. If installation succeded, you should now see

something similar to the following. By the way, “>>>” is the Python prompt.

Microsoft Windows [Version 10.0.16299.192]

(c) 2017 Microsoft Corporation. All rights reserved.

C:\Users\user>python

Python 3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)] on

win32

Type "help", "copyright", "credits" or "license" for more information.

>>>

8. Type Ctrl+Z and then [Enter] to exit Pyhton.

9. Close the Windows Command Prompt.

Prepration #2: Testing the Python Intepreter (Windows users only)

1. Plug in the USB flash drive containing the Python interpreter. Record the drive name (e.g. F). The following

assumes the drive name is “F”.

2. Open a Windows Command Prompt (not Python prompt).

3. Type md c:\cis247 and press [Enter] to create a new directory named “cis247” in the “C” drive. [Note: You

cannot create the same directory twice if the “C:\cis247” directory already exists.]

C:\Users\user>md c:\cis247

4. Type cd c:\cis247 and press [Enter] to change to the “cis247” directory.

C:\Users\user>cd c:\cis247

C:\cis247>

5. In the “cis247” directory, type notepad lab1_0.py and press [Enter] to use Notepad to create a new script

file named “lab1_0.py”.

C:\cis247>notepad lab1_0.py

6. Click Yes to confirm.

7. Enter the following Python statements. Be careful, it is case-sensitive.


print("Hello world!")

8. Type python lab1_0.py and press [Enter] to compile it. A sample ouput looks:

C:\cis247>python lab1_0.py

Hello World!


Learning Activity #1:

Windows OS Users Linux Users

1. Be sure to complete Preparation #1 and #2 before proceeding to

the next steps.

2. Launch the Windows Command Prompt.

3. In the prompt, type cd c:\cis247 and press [Enter] to change

to the “cis247” directory.

C:\Users\user>cd c:\cis247

4. Under the “cis247” directory, type python (or python3 for Linux

user) and press [Enter] to launch the Python interpreter. “>>>” is

the Python prompt.

E:\cis247>python

Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep 1 2017,

02:16:59) [MSC v.1900 32 bit (Intel)] on win32

Type "help", "copyright", "credits" or "license" for

more information.

>>>

1. Be sure to read Appendix B before

proceeding to the next step.

2. Boot into Linux, and then open a

Terminal Emulator.

3. Type cd ~/cis247 and press

[Enter] to change to the “~/cis247”

directory.

$ cd ~/cis247

4. In the shell prompt, type python3

and press [Enter].

$ python3 Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep

1 2017, 02:16:59) [GCC 7.1.1 20170802

(Ubuntu 7.1.1-7)] on Linux

Type "help", "copyright", "credits" or

"license" for more information.

>>>

5. In the Python prompt (“>>>”), type x=21 and press [Enter] to assign 21 to a variable named x.

>>> x=21

6. Type x and press [Enter] to ask the prompt to return the value of x.

>>> x

21

7. Type x = 12**2 and press [Enter] to assigns the value 122 (or 12 to the 2nd power) to a variable x.

>>> x = 12**2

8. Type x/2 and press [Enter] to return the calculation result of x/2.

>>> x/2

72.0

9. Type y = 4.35 and press [Enter] to assign a value 4.35 to a variable y.

>>> y = 4.35


10. Type y*2 and press [Enter] to return the value of y times 2.

>>> y*2

8.7

11. Type 5.231 * 6.172 * 29 and press [Enter] to calculate 5.231 × 6.172 × 29.

>>> 5.231 * 6.172 * 29

936.2862279999999

12. Type 2 + 6 and press [Enter] to calculate the sum of 2 + 6.

>>> 2 + 6

8

13. Type (3 + 1j) * (3 - 1j) and press [Enter] to calculate the product of two complex numbers.

>>> (3 + 1j) * (3 - 1j)

(10+0j)

14. Type 22 / 7 and press [Enter] to perform an integer division and observe how Python automatically change

the data type to float during the calculation.

>>> 22 / 7

3.142857142857143

15. In the Python prompt, type exit() and press [Enter] (or hold Ctrl and then press Z) to exit the Python

interpreter and return to Command Prompt.

>>> exit()

C:\cis247>

16. Under the “cis247” directory, type notepad lab1_1.py (or gedit lab1_1.py for Linux user) and press

[Enter] to create a new file named lab1_1.py in the E:\cis247 directory.

Windows OS Linux C:\cis247>notepad lab1_1.py

$ gedit lab1_1.py

17. Click Yes to the following pop-up window (Windows OS only).

18. In the editor (Notepad or “gedit”), type in the following contents to organize all the above statements into a

Python script. The script also demonstrates how the “str()” function works. By the way, “\n” means to add a

new line.


s = "Results:\n" # declare s as string

#example 1

x=21

s += str(x) + "\n" # + is cancatenation

#example 2

x = 12**2

s += str(x/2) + "\n"

#example 3

y = 4.35

s += str(y*2) + "\n"

#example 4

s += str(5.231 * 6.172 * 29) + "\n"

#example 5

s += str(2 + 6) + "\n"

#example 6

s += str((3 + 1j) * (3 - 1j)) + "\n"

#example 7

s += str(22 / 7) + "\n"

###### Message Box Code ######


root = Tk()



root.mainloop()

19. Save the file an exit the editor.

20. In the prompt, type python lab1_1.py and press [Enter].

21. A sample output looks like this:

22. Download the “assignment template”, and rename it to lab1.doc if necessary. Capture a screen shot similar to

the above and paste it to a Microsoft Word document named “lab1.doc” (or .docx).


1. Open a Windwos Command Prompt (or a Linux Terminal emulator).


2. For Windows users, change to the “X:\cis247” directory (where “X” is the drive name. The following steps use

“E” as example). For Linux users, type cd ~/cis247 and press [Enter] to change the “cis247” directory.

3. Under the “cis247” directory, type python (or python3 for Linux users) and press [Enter] to launch the

Python interpreter. “>>>” is the Python prompt.

Windows OS Linux C:\cis247> python $ python3

4. In the Python prompt (“>>>”), type print("Hello world!") and press [Enter] to use the print() function to

print a string.

>>> print("Hello world!")

Hello world!

5. Type print("Hello" + "world" + "!") and press [Enter]. Compare the output with the above one.

>>> print("Hello" + "world" + "!")

Helloworld!

6. Type print("Hello"[-1]) and press [Enter] to display the last character of the string.

>>> print("Hello"[-1])

o

7. Type fullname = "Taylor Swift" and press [Enter] to assign a string “Taylor Swift” to a variable

fullname.

>>> fullname = "Taylor Swift"

8. Type fullname and press [Enter] to return the value stored in the fullname variable.

>>> fullname

'Taylor Swift'

9. Type course = "Python Programming" and press [Enter] to assign a string to the course variable.

>>> course = "Python Programming"

10. Type course*2 and press [Enter] to print the value stored in the course variable twice.

>>> course*2

'Python ProgrammingPython Programming'

11. Type "apple" < "orang" and press [Enter] to compare the order of two strings. The “string” is listed ahead

of “orange”; therefore, the index of “apple” is less than the index of “orange”.

>>> "apple" < "orang"

True

12. Type "tree" == "Tree" and press [Enter] to check if theset two words are exactly the same character by

character.

>>> "tree" == "Tree"

False

13. Type "schools" > "school" and press [Enter] to check if the word “schools” is listed behind the word

“school”.


>>> "schools" > "school"

True

14. Type "Home" != "Home" and press [Enter] to check if these two words are not exactly the same.

>>> "Home" != "Home"

False

15. Type print("\a\a\a\a\a") and press [Enter] to produce five beep sounds.

>>> print("\a\a\a\a\a ")

16. Type print("\t\t\tWelcome to CIS247!") and press [Enter] to use the tab (“\t”).

>>> print("\t\t\tWelcome to CIS247!")

Welcome to CIS247!


interpreter and return to Command Prompt (or shell prompt of Linux).

18. In the “cis247” directory, use Notepad (or “gedit” for Linux user) to create a new file named lab1_2.py with the

following Python code. In this example, the instructor did not use the “str()” function.

s = "Results:\n"

#example 1

s += "Hello world!\n"

#example 2

s += "Hello" + "world" + "!\n"

#example 3

s += ("Hello"[-1]) + "\n"

#example 4

fullname = "Taylor Swift"

s += fullname + "\n"

#example 5

course = "Python Programming"

s += course*2 + "\n"

#example 6

s += str("apple" < "orang") + "\n"

s += str("tree" == "Tree") + "\n"

s += str("schools" > "school") + "\n"

s += str("Home" != "Home") + "\n"

#example 7

s += ("\a\a\a\a\a") + "\n"

#example 8

s += "\t\t\tWelcome to CIS247!\n"



root = Tk()




root.mainloop()

19. In the prompt, type python lab1_2.py and press [Enter] to test the program. You should hear a “beep” from

the computer.

20. Capture a screen shot similar to the above and paste it to a Microsoft Word document named “lab1.doc”

(or .docx).


1. Open a Windows Command Prompt (or Terminal Emulator for Linux user).

2. Change to the “cis247” directory.

3. Under the “cis247” directory, type python (or python3 for Linux user) and press [Enter] to launch the Python

interpreter. “>>>” is the Python prompt.

4. Type the following Python statements, one at a time, to calculate the total dollar amount.

>>> unit_price = 5.75

>>> qty = 12

>>> print("$", unit_price * qty)

$ 69.0

5. Type the following Python statements, one at a time, to calculate 1+2+3+4+5.

>>> x = 1

>>> x = x + 2

>>> x = x + 3

>>> x = x + 4

>>> x = x + 5

>>> print(x)

15

6. Type print("Python", "3", " ", "programming") and press [Enter] to concatenate strings using the

print() function.

>>> print("Python", "3", " ", "programming")

Python 3 programming

7. Type print("Python" "3" " " "programming") and press [Enter] to concatenate strings using the print()

function. Compare the result with the above one.

>>> print("Python" "3" " " "programming")

Python3 programming


8. Type the following Python statements, one at a time, to use the int() function to convert a numerical value

from floating-point to integer.

>>> x = 3.14

>>> int(x)

3

9. Type the following Python statements, one at a time, to convert a string type to float type using the float()

function.

>>> y = "0.5382" # y is string

>>> y # y is string

'0.5382'

>>> print(float(y)) # y is float

0.5382


interpreter and return to Command Prompt.

11. In the “cis247” directory, use Notepad (or “gedit”) to create a new file named lab1_3.py with the following

Python code.

s = "Results:\n"

# example 1

unit_price = 5.75

qty = 12

s += "$" + str(unit_price * qty) + "\n"

#example 2

x = 1

x = x + 2

x = x + 3

x = x + 4

x = x + 5

s += str(x) + "\n"

#example 3

s += "Python" + "3" + " " + "programming\n"

#example 4

s += """Python" "3" " " "programming\n"""

#example 5

x = 3.14

s += str(int(x)) + "\n"

#example 6

y = "0.5382" # y is string

s += str(float(y)) + "\n" # y is float



root = Tk()



root.mainloop()


12. Type python lab1_3.py and press [Enter] to test the program. A sample outcome looks:


(or .docx).



2. Change to the “cis247” directory, and then launch the Python intepreter.

3. Type the following Python statements, one at a time, to observe how multiline statement works.

>>> x = 5

>>> if x > 3:


...

Correct!


>>> x = 15

>>> if (x/3 > 6):


... else:

... print("Wrong!")

...

Wrong!


>>> y = (0, 1, 2, 3, 4, 5)

>>> for n in y:

... print(n)

...

0

1

2

3

4

5

6. Type the following Python statements, one at a time, to observe how multiline statement works. Notice that

when n is 2, the value of 2*2 is returned.

>>> z = (0, 1, 2, 3, 4, 5)

>>> for n in z:

... if n == 2:

... print(n*n)

... else:

... print(n)

...


0

1

4

3

4

5

7. Type the following Python statements, to use semicolon to combine multiple statements into one single-line

statement.

>>> w = 6; x = 5; y = 3; z = 7;

>>> print(w, x, y, z)

6 5 3 7

8. Type the following Python statements, to use the continuation character (\) to combine multiple statements into

one single-line statement.

>>> 1 + 2 + 3 + 4 \

... + 5 + 6 \

... + 7 + 8 + 9

45

9. Type the following Python statements, to use the continuation character (\) to combine multiple statements into

one single-line statement.

>>> "An" + " apple a day " + \

... "keeps doctors" + " " + \

... "away."

'An apple a day keeps doctors away.'

10. Type the following Python statements, to enclose multiple lines of statement with a pair of parentheses.

>>> (1 + 2 + 3 +

... 4 + 5 + 6 +

... 7 + 8 + 9)

45

11. Type the following Python statements, to enclose multiple lines of statement with a pair of square brackets.

>>> [1 + 2 + 3 +

... 4 + 5 + 6 +

... 7 + 8 + 9]

[45]

12. Type the following Python statements, to define multiple lines of statement with a pair of curly braces. Notice

that these statements define a Python directory.

>>> months = {'01':'January', '02':'February', '03':'March',\

... '04':'April', '05':'May', '06':'June', \

... '07':'July', '08':'August', '09':'September', \

... '10':'October', '11':'November', '12':'December'}

>>> print(months)


following Python code. Pay close attention to the indent.

s = "Results:\n"

# example 1

x = 5


if x > 3:

s += "Correct!\n"

# example 2

x = 15

if (x/3 > 6):

s += "Correct!\n"

else:

s += "Wrong!\n"

#example 3

y = (0, 1, 2, 3, 4, 5)

for n in y:

s += str(n) + " "

s += "\n"

#example 4

z = (0, 1, 2, 3, 4, 5)

for n in z:

if n == 2:

s += str(n*n) + " "

else:

s += str(n) + " "

s += "\n"

#example 5

w = 6; x = 5; y = 3; z = 7;

s += str(print(w, x, y, z)) + "\n"

#example 6

s += str(1 + 2 + 3 + 4 \

+ 5 + 6 \

+ 7 + 8 + 9) + "\n"

#example 7

s += str(1 + 2 + 3 +

4 + 5 + 6 +

7 + 8 + 9) + "\n"

#example 8

s += str([1 + 2 + 3 +

4 + 5 + 6 +

7 + 8 + 9]) + "\n"

#example 9

months = {'01':'January', '02':'February', '03':'March',\

'04':'April', '05':'May', '06':'June', \

'07':'July', '08':'August', '09':'September', \

'10':'October', '11':'November', '12':'December'}

s += str(months)



root = Tk()



root.mainloop()

14. Type python lab1_4.py to execute the program. A sample output looks (6 5 3 7 are displayed in the

console):



(or .docx).


1. User the web browser to download the “inout.zip” file and extract both “MessgeBox.py” and “InputBox.py”

files to the “cis247”directory.


3. Change to the “cis247” directory, and then launch the Python intepreter.


following Python code. This script is an implementation of C=(F-32)×5

9

import InputBox

InputBox.ShowDialog("Enter the 1st Fahrenheit value:")


c1 = (float(f) - 32) * (5/9)

InputBox.ShowDialog("Enter the 2nd numberFahrenheit value:")


c2 = (float(f) - 32) * (5/9)

import MessageBox

MessageBox.Show(str(c1) + "\n" + str(c2))

5. Type python lab1_5.py to execute the program. A sample output looks:

and


(or .docx).

Submittal

1. Upon the completion of learning activities, use Windows Compressed (zipped) Folder or Winzip to compress

the following files and name the zipped file lab1.zip:

• lab1_1.py

• lab1_2.py

• lab1_3.py

• lab1_4.py

• lab1_5.py

• lab1.doc (or .docx)


2. Upload it to Question 11 as response (available at http://cypresscollege.blackboard.com) as response.

Programming Exercise #01:

1. Create a Python source file named “ex01.py” that will include the following two lines. Be sure to replace

YourNameHere with your full name.

# Student: YourNameHere

# Programming Exercise: 01

2. Next to the above lines, use the “Message Box Code” (as shown it in learning activity #1~4) to write a

functioning Python code that will produce the following outputs. Be sure to replace YourNameHere with your

full name. [Hint: use “\n” to insert blank lines]

3. Download the “programming exercise template”, and rename it to ex01.doc. Capture a screen shot similar to the

above figure(s) and paste it to a Microsoft Word document named ex01.doc (or ex01.docx).

4. Compress both ex01.py and ex01.doc (or ex01.docx) to a .zip file named ex01.zip.

5. Upload the ex01.py file as response of Question 12.

Note: Your code must be fully functional to earn the credit. No partial credit is given. You will receive zero points if

either .py or .doc (or .docx) file is not submitted.

Appendix A:

1. Use the text editor (such as “Notepad” or “gedit”) to create a new file named “InputBox.py” with the following

content:

####File name: InputBox.py

import tkinter


root = Tk()

e1 = Entry(root, width=55)

result = ""

def ShowDialog(s):

root.title("Input Box")

root.geometry("355x100+30+30")

Label(root, justify=LEFT, text = s).grid(row=0, column=1, sticky=W, padx= 10,

pady=5)

e1.grid(row=1, column=1, padx= 10, pady=5)

button1 = Button(root, text=" OK ", command = button1_Click)

button1.grid(row=2, column=1, sticky=E, padx= 10, pady=5)

root.mainloop()

def button1_Click():

f = open('tttemp', 'w')


f.write(e1.get())

f.close()

e1.delete(0,END)

root.quit()

def GetInput():

f = open('tttemp', 'r')

result = f.read()

f.close()

import os

os.remove('tttemp')

return result

2. Use the text editor (such as “Notepad” or “gedit”) to create a new file named “MessageBox.py” with the

following content:

#File name: MessageBox.py

import tkinter


def Show(str):

root = Tk()


Label(root, justify=LEFT, text = str).grid()

root.mainloop()

3. Keep both “MessageBox.py” and “InputBox.py” files. You will frequently use them throughout this course.

Appendix B: Installing Live USB Ubuntu

1. In a Windows 10 machine, use a web browser to visit the https://www.ubuntu.com/download/desktop site.

2. Download the latest .ISO versio of Ubuntu (As of Feburary, 2018, it is 17.10.1). The file name is similar to

“ubuntu-17.10.1-desktop-amd64.iso”, and the file size is approximately 1.5GB.

3. Use a browser to visit the https://rufus.akeo.ie/ site.

4. Download the latest version of “Rufus” (as of Jan 2018, it is Rufus 2.18 and the file name is “rufus-2.18.exe”).

5. Insert the “non-persisten” USB drive to a port. Record its drive name (such as. “E”).

6. Launch Rufus. A window similar to the following appears.


7. Verify that the “Device” column is pointed to the correct drive (such as. “E”).

8. Click the “folder” icon and locate the Ubuntu ISO file” (e.g. ubuntu-17.10.1-desktop-amd64.iso).

9. Click Start.

10. Click OK on the following warning windows.

and

11. Wait till the writing completes. Capture a screen shot similar to the following and named it “ex01.png”. Upload

only this file to Question 12 of Assignment.

12. Use the newly re-created “non-persistent” USB drive to boot into Linux.

13. After the desktop is fully loaded, click “Try Ubuntu”.


14. In the Ubuntu desktop, press Ctrl + Alt + T to launch the “Terminal” which is a command-line interface

containing the prompt. The following is a sample shell prompt with a prompt sign ($).

ubuntu@ubuntu:~$

15. In the prompt, type python3 and press [Enter] to launch python.

ubuntu@ubuntu:~$ python3

Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep 1 2017, 02:16:59) [GCC 7.1.1 20170802

(Ubuntu 7.1.1-7)] on Linux


>>>

16. Press Ctrl-Z to exit Python and return to Linux shell prompt.

17. With access to Internet, type sudo apt-get install python3-tk and press [Enter] to install the “tk”

module.

$ sudo apt-get install python3-tk

18. Type gedit lab1_0.py and press [Enter] to use the “gedit” to create a new file named “lab1_0.py”, with the

following content.

s = "Hello world!"



root = Tk()



root.mainloop()

19. Exit the “gedit” and return to the shell prompt.

20. Type python3 lab1_0.py and press [Enter]. If all configuration are done successfully, you should now see a

pop-up window similar to the following.

21. Proceed to learning activity #1.

Appendix C: Copy entire Python directory to a USB flash drive (For Windows users only)

1. Plug in the USB drive. Record the assigned drive name (e.g. “F”).


2. Copy the entire “python-32” directory to a USB flash drive and rename it to “python36”.

3. Open the Command Prompt, type X: and press [Enter] to change to the flash drive (replace “X” with the correct

drive name). The following uses “F” as example.

C:\Users\user>F:

F:\>

4. Type notepad runpython.bat and press [Enter] to use Notepad to create a batch file named “setup.bat”.

F:\>notepad runpython.bat

5. Click Yes to confirm.

6. Enter the following DOS command.

path=%path%;%CD%python36;

7. Save the file and exit Notepad. You should now return to the Command Prompt.

F:\>

8. Type runpython.bat to set the path. Depending on the current settings of the machine, the output varies.

However, make sure the X:\python36 path is appended, as shown below.

F:\>runpython.bat

F:\>path=C:\Windows\system32;........;F:\python36;

9. Type python (or python3 for Linux user) and press [Enter] to test the settings. The installation succeeds if

something similar to the following appears. Notice that “>>>” is the Python prompt.

F:\>python

Python 3.6.2 (v3.6.2:37dagde53fg8s9, Sep 1 2017, 02:16:59) [MSC v.1900 32 bit

(Intel)] on win32


>>>

10. Press Control + Z and then [Enter] to terminate the python interpreter and return to the Command Prompt.

F:\>


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