python english

7/25/2019 Python English

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Python

1. Introduction :

Our first program : helle word

print("Hello, world! My name is "type your name")

comments :

# This is the comment for the comments.py fileprint("Hello!") # this comment is for the second line

print("# this is not a comment")# add new comment here

2. Variables

Variable definition

a = b = 2 # This is called a "chained assignment". It assignsthe value 2 to variables "a" and "b".print("a = " + str(a)) # We'll explain the expression stra!

later in the course. or now it is used to convert thevariable "a" to a string.print("b = " + str(b))

greetings = "greetings"print("greetings = " + str(greetings))greetings = another valueprint("greetings = " + str(greetings))

Undefined variable

variable = 1

print(other variable)

variable type

variable = 1print(other variable)


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type conversion

type_cast

number = 9

print(type(number)) # print type of variable "number"

float_number = 9.0

print(float_number)print(Convert float_number to integer)

arithmetic_operator

number = 9.0 # float number

result = divide 'number' by to

remainder = !al!ulate the remainder

print("result = " + str(result))print("remainder = " + str(remainder))

assignment

number = 9.0print("number = " + str(number))

number "= 2print("number = " + str(number))

number operator #

print("number = " + str(number))

boolean_operator

to = 2three = $

is_e%ual = to operator three

print(is_e%ual)


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comparaison_operator

one = 1to = 2three = $

print(one & to & three) # This chained comparison means thatthe one two! and two three! comparisons are performed atthe same time.

is_greater = three operator to

print(is_greater)

3. tring

!oncatenation

hello = "Hello"orld = 'World'

hello_orld = type here

print(hello_orld) # $ote% you should print "&ello World"

string_multiplication

hello = "hello"ten_of_hellos = hello operator 10print(ten_of_hellos)

string_inde"ing

python = "Python"print("h " + python'$) # $ote% string indexing startswith

p_letter = type here

print(p_letter)

negative_inde"ing

long_string = "his is a ery long string!"e!lamation = type hereprint(e!lamation)


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string slicing

monty_python = "Monty Python"monty = monty_python'*# # one or both index could bedropped. monty(python)%*+ is e,ual to monty(python)%*+

print(monty)python = type hereprint(python)

in_operator

i!e_!ream = "ice cream"print("cream" in i!e_!ream) # print boolean result directly

!ontains = type here

print(!ontains)

string length

len_function

phrase = """t is a really long stringtriple$uoted strings are used

to de%ine multiline strings"""first_half = type hereprint(first_half)

character_escaping

dont_orry = "&on't worry about apostrophes"print(dont_orry)print("he name o% this icecream is "(weeet"")

print('tet')

string_methods

monty_python = "Monty Python"print(monty_python)

print(monty_python.loer()) # print lower-cased version ofthe string

print(upper !ased monty_python)


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string_formating

name = "*ohn"print("Hello, Py+harm! My name is s!" name) # $ote% sis inside the string/ is after the string

print("'m special symbol years old" years)

#. $ata structure

%ists introduction

s%uares = '1, -, 9, 1, 2# # create new listprint(s%uares)

print(sli!e)

lists operations

animals = ''elephant', 'lion', 'tiger', "gira%%e" # createnew listprint(animals)

animals += '"mon-ey", 'dog' # add two items to the listprint(animals)

animals.append("dino") # add one more item to the list usingappend! methodprint(animals)

repla!e 'dino'with 'dinosaur'print(animals)

list item

animals = ''elephant', 'lion', 'tiger', "gira%%e", "mon-ey",'dog' # create new listprint(animals)

animals'1*$ = ''cat' # replace 2 items -- 'lion' and'tiger' with one item -- 'cat'print(animals)

animals'1*$ = ' # remove 2 items -- 'cat' and 'giraffe'from the listprint(animals)


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!lear list

print(animals)

uple

alphabet = ('a', 'b', 'c', 'd', 'e', '%', 'g', 'h', 'i', '.','-', 'l', 'm', 'n', 'o', 'p', '$', 'r', 's', 't', 'u', '', 'w', '', 'y','/')

print(alphabet length)

&ictionaries

# create new dictionary.phone_boo/ = "*ohn"* 12$, "*ane"* 2$-, "*erard"* $-# #

"0ohn"/ "0ane" and "0erard" are 1eys and numbers are valuesprint(phone_boo/)

# dd new item to the dictionaryphone_boo/'"*ill" = $-#print(phone_boo/)

# 3emove 1ey-value pair from phone(boo1del phone_boo/''*ohn'

print(ane's phone)

$ictionary &eys '( and values'(

phone_boo/ = "*ohn"* 12$, "*ane"* 2$-, "*erard"* $-# #create new dictionaryprint(phone_boo/)

# dd new item to the dictionaryphone_boo/'"*ill" = -#

print(phone_boo/)

print(phone_boo/./eys())

print(phone_boo/ values)

In &ey)ord

gro!ery_list = '"%ish", "tomato", 'apples' # create newlist

print("tomato" in gro!ery_list) # chec1 that grocery(listcontains "tomato" item


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gro!ery_di!t = "%ish"* 1, "tomato"* , 'apples'* $ #create new dictionary

print(is '%ish' in gro!ery_di!t /eys)

*. !ondition e"pressions

+oolean operators

name = "*ohn"age = 13

print(name == "*ohn" or age == 13) # chec1s that eithername e,uals to "0ohn" 43 age e,uals to 56

print(ohn is not 2$ years old)

+oolean operators order


print(name == "*ohn" or not age 4 13)

print("name" is "0llis" or not ("name" e%ual "*ohn" and he is13 years old))

If statement


i% name == "*ohn" or age == 13* # chec1 that name is "0ohn"or age is 56. If so print next 2 lines.

print("name is *ohn") print("*ohn is 12 years old")

tas/s = ''tas-1', 'tas-3' # create new list

!he!/ i% 'tas-s' is empty print("empty")


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,lse- elif part in if statement

= 25

i% & 0*

print(' 4 5') # executes only if x eli% == 0* print(' is /ero') # if it's not true thatx / chec1 if x 77 eli% == 1* print(' == 1') # if it's not true thatx and x 87 / chec1 if x 77 5else* print('non o% the aboe is true')

name = "*ohn"

!he!/ i% name e%ual to "*ohn" print(6rue)otherise print(7alse)

. %oops

/or loop

%or i in range(#)* # for each number i in range -9.range*! function returns list )/ 5/ 2/ :/ 9+ print(i) # this line is executed * times. irsttime i e,uals / then 5/ ...

primes = '2, $, #, 3 # create new list

iterate over primes using %or loop print(prime)

/or loop using string

hello_orld = "Hello, World!"

%or !h in hello_orld* # print each character fromhello(world print(!h)

length = 0 # initiali;e length variable

!ount ho many !hara!ters are in the hello_orld using loop length += 1 # add 5 to the length on each iteration


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print(len(hello_orld) == length)

)hile loop

s%uare = 1

while s%uare &= 10* print(s%uare) # This code is executed 5 times s%uare += 1 # This code is executed 5 times

print("6inished") # This code is executed once

s%uare = 0number = 1

print all s%uares %rom 0 to 99 s%uare = number 88 2 print(s%uare) number += 1

brea& &ey)ord

!ount = 0

while 6rue* # this condition cannot possibly be false print(!ount) !ount += 1 i% !ount 4= #* brea- # exit loop if count


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continue &ey)ord

%or i in range(#)* i% i == $* continue # s1ip the rest of the code inside loop for

current i value print(i)

%or in range(10)* i% Che!/ i% is even* continue # s1ip printx! for this loop print()

0. /unctions

$efinition

de% hello_orld()* # function named my(function print("Hello, World!")

%or i in range(#)* hello_orld() # call function defined above * times

print(' want to be a %unction')print(' want to be a %unction')print(' want to be a %unction')

define a fun!tion named '%un' to repla!e three lines above print(' want to be a %unction')

%or i in range($)* fun()

parameter and call argument

de% foo()* # x is a function parameter print(" = " + str())

foo(#) # pass * to foo!. &ere * is an argument passed tofunction foo.

define a fun!tion named 's$uare' that prints s%uare of passedparameter print( 88 2)

s%uare(-)s%uare(5)


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s%uare(1#)s%uare(2$)s%uare(-2)

return value

de% sum_to_numbers(a, b)* return a + b # return result to the functioncaller

! = sum_to_numbers($, 12) # assign result of functionexecution to variable 'c'

de% fib(n)*

"""This is documentation string for function. It'll beavailable by fib.((doc((! 3eturn a list containing the ibonacci series up to n.""" result = ' a = 0 b = initialie variable b while a & n* result.append(a) tmp_var = b update variable b update variable a

return result

print(fib(10))

default parameter

de% multiply_by(a, b=2)* return a 8 b

print(multiply_by($, -3))print(multiply_by($)) # call function using default valuefor b parameter

de% hello(add parameters %or fun!tion, set default value %orname)* print("Hello s! My name is s" (sub:e!t, name))

hello("Py+harm", "*ane") # call 'hello' function with"=y>harm as a sub?ect parameter and "0ane" as a name

hello("Py+harm"

) # call 'hello' function with"=y>harm as a sub?ect parameter and default value for the name


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. !lass and obect

$efinition

class ;yClass*

variable = assign any value to variable

de% foo(self)* # we'll explain self parameter later intas1 9 print("Hello %rom %unction %oo")

my_ob:e!t = ;yClass() # variable "my(ob?ect" holds an ob?ectof the class "@y>lass" that contains the variable and the"foo" function

Variable access

class ;yClass* variable1 = 1 variable2 = 2

de% foo(self)* # we'll explain self parameter later intas1 9 print("Hello %rom %unction %oo")

my_ob:e!t = ;yClass()my_ob:e!t1 = ;yClass()

my_ob:e!t.variable2 = $ # change value stored in variable2in my(ob?ect

print(my_ob:e!t.variable2)print(my_ob:e!t1.variable2)

my_ob:e!t.foo() # call method foo! of ob?ect my(ob?ect

print(value of variable1 %rom my_ob:e!t)


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Variable access

class Car* !olor = "" de% des!ription(self)*

des!ription_string = "his is a s car7" self.!olor# we'll explain self parameter later in tas1 9 return des!ription_string

!ar1 = Car()!ar2 = !reate ob:e!t of Car

!ar1.!olor = "blue"set !ar2 !olor

print(!ar1.des!ription())

print(!ar2.des!ription())

self e"planation

class Comple* de% !reate(self, real_part, imag_part)* self.r = real_part self.i = imag_part

class Cal!ulator* !urrent = 0

de% add(self, amount)* add number to !urrent

de% get_!urrent(self)* return self.!urrent

special_init_method

class


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parameter explicitly/ only color parameter

print(!ar.!olor)

. 4odules 5 pac&ages

Import module

!alculator.py

"""This module contains >alculator class"""

class Cal!ulator* de% __init__(self)* self.!urrent = 0

de% add(self, amount)* self.!urrent += amount


Import.py

import !al!ulator

!al! = !al!ulator.Cal!ulator() # create new instance of>alculator class defined in calculator module!al!.add(2)

print(!al!.get_!urrent())

here import my_module

!all fun!tion hello_orld %rom my_module

my_module.py

import !al!ulator

!al! = !al!ulator.Cal!ulator() # create new instance of


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>alculator class defined in calculator module!al!.add(2)


here import my_module

!all fun!tion hello_orld %rom my_module

builtin modules

import datetime

print(!urrent date)

from import

calculator.py

"""This module contains >alculator class"""

class Cal!ulator* de% __init__(self)* self.!urrent = 0

de% add(self, amount)* self.!urrent += amount


/rom_import.py

%rom !al!ulator import Cal!ulator

!al! = Cal!ulator() # here we can use >alculator classdirectly without prefix calculator.!al!.add(2)


import hello_orld %rom my_module

print(hello_orld()) # $ote% hello(world function used

without prefix


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9rite_to_file.py

oo = ''lion', "elephant", 'mon-ey'

i% __name__ == "main"*

f = open("output7tt", add modifier)

%or i in oo* add the hole oo to the output.tt

!lose the file

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