8/12/2019 Program Img

1/4

Programimg

The programming language is going to define sin taxis and semantics

Low level language: move data from one location to another, program basically level machine.

High level language: Uses more abstract term, invert a matrix, compute a function

Compiled language: The abstractions are converted back into low level abstraction, then executed

Interpreted language: Special program converts source code to internal data structure, then

interpreter sequentially converts each step into low level machine instruction and executes.

Python objects.

Program (or script) is a sequence of definitions and commands.

Objects.

Programs will manipulate data objects.

Each object has a type that defines the kinds of things programs can do to it

Objects are:

Scalar

int: integers, 5,100, 2563 float: real numbers, 2.0, 25.03, 3.14

Non scalar

Expressions

Operators on ints and floats

Sum +. Int + int = int float+ (int/float) = float

Difference -

Product *

Division / : must be 3.0 one float al least

**,

8/12/2019 Program Img

2/4

=

== equal

!= not equal

Boolean VALUES

A and B is true if both are True

A or B is true if both are True

Not A is true if A if false, and false if A is true

Convert int to float float (3)

True or false = true

False or false = false

Strings. str

Len = length

Indexing

abcd [0] 0 indicates the number that the object occupies in the string, so the number 0 I the

letter a, 1 is b and so and so..

abc [-1] returns c. because starts in 0 , and from the last counts -1 , -2 etc.

Slicing

If s is a string the expression s[start:end] denotes the substring that starts at star and ends at end -

1

"abcd"[2:]

the string is abcd

the first element "abcd"[0] is "a"

8/12/2019 Program Img

3/4

the third element "abcd"[2] is "c"

the use of : with nothing after it means "until the end"

so "abcd"[2:] is going to start with element 3 and continue until the string

ends.

Comands

Print

Raw_input

y = float (raw_input('Enter a number: '))

print (y*y)

area del rectangulo

print ('area de un rectangualo')

base = float (raw_input('base: '))

altura = float (raw_input('altura: '))

print (base*altura)

Branching programs,

Conditional

x = int(raw_input('Enter an integer: '))

if x%2 == 0:

print('')

print('Even')

else:

print('')

8/12/2019 Program Img

4/4

print('Odd')

print( 'Done with conditional' )

x = int(raw_input('Enter an integer: '))

if x%2 == 0:

if x%3 == 0:

print('Divisible by 2 and 3')

else:

print('Divisible by 2 and not by 3')

elif x%3 == 0:

print( 'Divisible by 3 and not by 2' )

else:

print ('not divisible by 2 and 3')

if type(varA) == str or type(varB) == str:

print ('string involved')

elif varA == varB:

print('equal')

elif varA > varB:

print('bigger')

else:

print('smaller')