• Python (Python.org)
• Learn X in Y minutes (learnxinyminutes.com)

>>> print("Hello, World!")
        Hello, World!
        

The famous "Hello World" program in Python

age = 18      # age is of type int
        name = "Ram" # name is now of type str
        print(name)
        

Python can't declare a variable without assignment.

>>> msg = "Hello, World!"
        >>> print(msg[2:5])
        hello ,world
        

See: Strings

mylist = []
        mylist.append(1)
        mylist.append(2)
        for item in mylist:
        print(item) # prints out 1,2
        

See: Lists

num = 200
        if num > 0:
        print("num is greater than 0")
        else:
        print("num is not greater than 0")
        

See: Flow control

for item in range(6):
        if item == 3: break
        print(item)
        else:
        print("Finally finished!")
        

See: Loops

>>> def my_function():
        ...     print("Hello from a function")
        ...
        >>> my_function()
        Hello from a function
        

See: Functions

result = 10 + 30 # => 40
        result = 40 - 10 # => 30
        result = 50 * 5  # => 250
        result = 16 / 4  # => 4.0 (Float Division)
        result = 16 // 4 # => 4 (Integer Division)
        result = 25 % 2  # => 1
        result = 5 ** 3  # => 125
        

The / means quotient of x and y, and the // means floored quotient of x and y, also see StackOverflow

counter = 0
        counter += 10           # => 10
        counter = 0
        counter = counter + 10  # => 10
        
        message = "Part 1."
        
        # => Part 1.Part 2.
        message += "Part 2."   
        

>>> website = 'CareerInEdu.com'
        >>> f"Hello, {website}"
        "Hello, CareerInEdu.com"
        
        >>> num = 10
        >>> f'{num} + 10 = {num + 10}'
        '10 + 10 = 20'
        

See: Python F-Strings

hello = "Hello World"
        hello = 'Hello World'
        
        multi_string = """Multiline Strings
        Lorem ipsum dolor sit amet,
        consectetur adipiscing elit """
        

See: Strings

x = 1    # int
        y = 2.8  # float
        z = 1j   # complex
        
        >>> print(type(x))
        <class 'int'>
        

my_bool = True 
        my_bool = False
        
        bool(0)     # => False
        bool(1)     # => True
        

list1 = ["apple", "banana", "cherry"]
        list2 = [True, False, False]
        list3 = [1, 5, 7, 9, 3]
        list4 = list((1, 5, 7, 9, 3))
        

See: Lists

my_tuple = (1, 2, 3)
        my_tuple = tuple((1, 2, 3))
        

Similar to List but immutable

set1 = {"a", "b", "c"}   
        set2 = set(("a", "b", "c"))
        

Set of unique items/objects

>>> empty_dict = {}
        >>> a = {"one": 1, "two": 2, "three": 3}
        >>> a["one"]
        1
        >>> a.keys()
        dict_keys(['one', 'two', 'three'])
        >>> a.values()
        dict_values([1, 2, 3])
        >>> a.update({"four": 4})
        >>> a.keys()
        dict_keys(['one', 'two', 'three', 'four'])
        >>> a['four']
        4
        

Key: Value pair, JSON like object

#Integers

x = int(1)   # x will be 1
        y = int(2.8) # y will be 2
        z = int("3") # z will be 3
        

#Floats

x = float(1)     # x will be 1.0
        y = float(2.8)   # y will be 2.8
        z = float("3")   # z will be 3.0
        w = float("4.2") # w will be 4.2
        

#Strings

x = str("s1") # x will be 's1'
        y = str(2)    # y will be '2'
        z = str(3.0)  # z will be '3.0'
        

>>> hello = "Hello, World"
        >>> print(hello[1])
        e
        >>> print(hello[-1])
        d
        

Get the character at position 1 or last

>>> for char in "foo":
        ...     print(char)
        f
        o
        o
        

Loop through the letters in the word "foo"

>>> hello = "Hello, World!"
        >>> print(len(hello))
        13
        

The len() function returns the length of a string

>>> s = '===+'
        >>> n = 8
        >>> s * n
        '===+===+===+===+===+===+===+===+'
        

>>> s = 'spam'
        >>> s in 'I saw spamalot!'
        True
        >>> s not in 'I saw The Holy Grail!'
        True
        
        

>>> s = 'spam'
        >>> t = 'egg'
        >>> s + t
        'spamegg'
        >>> 'spam' 'egg'
        'spamegg'
        

>>> name = input("Enter your name: ")
        Enter your name: Sita
        >>> name
        ' Sita'
        

Get input data from console

>>> "#".join(["Ram", "Peter", "Vicky"])
        'Ram#Peter#Vicky'
        

>>> "Hello, world!".endswith("!")
        True
        

>>> website = 'Careerinedu.com'
        >>> f"Hello, {website}"
        "Hello, Careerinedu.com"
        
        >>> num = 10
        >>> f'{num} + 10 = {num + 10}'
        '10 + 10 = 20'
        
        >>> f"""He said {"I'm Ram"}"""
        "He said I'm Ram"
        
        >>> f'5 {"{stars}"}'
        '5 {stars}'
        >>> f'{{5}} {"stars"}'
        '{5} stars'
        
        >>> name = 'Max'
        >>> age = 27
        >>> f"""Hello!
        ...     I'm {name}.
        ...     I'm {age}."""
        "Hello!\n    I'm Max.\n    I'm 27."
        

it is available since Python 3.6, also see: Formatted string literals

>>> f'{"text":10}'     # [width]
        'text      '
        >>> f'{"test":*>10}'   # fill left
        '******test'
        >>> f'{"test":*<10}'   # fill right
        'test******'
        >>> f'{"test":*^10}'   # fill center
        '***test***'
        >>> f'{12345:0>10}'    # fill with numbers
        '0000012345'
        

>>> f'{10:b}'        # binary type
        '1010'
        >>> f'{10:o}'        # octal type
        '12'
        >>> f'{200:x}'       # hexadecimal type
        'c8'
        >>> f'{200:X}'
        'C8'
        >>> f'{345600000000:e}' # scientific notation
        '3.456000e+11'
        >>> f'{65:c}'       # character type
        'A'
        >>> f'{10:#b}'      # [type] with notation (base)
        '0b1010'
        >>> f'{10:#o}'
        '0o12'
        >>> f'{10:#x}'
        '0xa'
        

>>> f'{-12345:0=10}'  # negative numbers
        '-000012345'
        >>> f'{12345:010}'    # [0] shortcut (no align)
        '0000012345'
        >>> f'{-12345:010}'
        '-000012345'
        >>> import math       # [.precision]
        >>> math.pi
        3.141592653589793
        >>> f'{math.pi:.2f}'
        '3.14'
        >>> f'{1000000:,.2f}' # [grouping_option]
        '1,000,000.00'
        >>> f'{1000000:_.2f}'
        '1_000_000.00'
        >>> f'{0.25:0%}'      # percentage
        '25.000000%'
        >>> f'{0.25:.0%}'
        '25%'
        

>>> f'{12345:+}'      # [sign] (+/-)
        '+12345'
        >>> f'{-12345:+}'
        '-12345'
        >>> f'{-12345:+10}'
        '    -12345'
        >>> f'{-12345:+010}'
        '-000012345'
        

>>> li1 = []
        >>> li1
        []
        >>> li2 = [4, 5, 6]
        >>> li2
        [4, 5, 6]
        >>> li3 = list((1, 2, 3))
        >>> li3
        [1, 2, 3]
        >>> li4 = list(range(1, 11))
        >>> li4
        [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
        

>>> li = []
        >>> li.append(1)
        >>> li
        [1]
        >>> li.append(2)
        >>> li
        [1, 2]
        >>> li.append(4)
        >>> li
        [1, 2, 4]
        >>> li.append(3)
        >>> li
        [1, 2, 4, 3]
        

>>> li = ['bread', 'butter', 'milk']
        >>> li.pop()
        'milk'
        >>> li
        ['bread', 'butter']
        >>> del li[0]
        >>> li
        ['butter']
        

>>> li = ['a', 'b', 'c', 'd']
        >>> li[0]
        'a'
        >>> li[-1]
        'd'
        >>> li[4]
        Traceback (most recent call last):
        File "<stdin>", line 1, in <module>
        IndexError: list index out of range
        

>>> li = [3, 1, 3, 2, 5]
        >>> li.count(3)
        2
        

>>> li = ["re"] * 3
        >>> li
        ['re', 're', 're']
        

num = 5
        if num > 10:
        print("num is totally bigger than 10.")
        elif num < 10:
        print("num is smaller than 10.")
        else:
        print("num is indeed 10.")
        

>>> a = 330
        >>> b = 200
        >>> r = "a" if a > b else "b"
        >>> print(r)
        a
        

value = True
        if not value:
        print("Value is False")
        elif value is None:
        print("Value is None")
        else:
        print("Value is True")
        

primes = [2, 3, 5, 7]
        for prime in primes:
        print(prime)
        

Prints: 2 3 5 7

animals = ["dog", "cat", "mouse"]
        # enumerate() adds counter to an iterable
        for i, value in enumerate(animals):
        print(i, value)
        

Prints: 0 dog 1 cat 2 mouse

x = 0
        while x < 4:
        print(x)
        x += 1  # Shorthand for x = x + 1
        

Prints: 0 1 2 3

x = 0
        for index in range(10):
        x = index * 10
        if index == 5:
            break
        print(x)
        

Prints: 0 10 20 30 40

for index in range(3, 8): 
        x = index * 10
        if index == 5:
            continue
        print(x)
        

Prints: 30 40 60 70

for i in range(4):
        print(i) # Prints: 0 1 2 3
        
        for i in range(4, 8):
        print(i) # Prints: 4 5 6 7
        
        for i in range(4, 10, 2):
        print(i) # Prints: 4 6 8
        

words = ['Mon', 'Tue', 'Wed']
        nums = [1, 2, 3]
        # Use zip to pack into a tuple list
        for w, n in zip(words, nums):
        print('%d:%s, ' %(n, w))
        

Prints: 1:Mon, 2:Tue, 3:Wed,

nums = [60, 70, 30, 110, 90]
        for n in nums:
        if n > 100:
            print("%d is bigger than 100" %n)
            break
        else:
        print("Not found!")
        

Also see: Python Tips

def hello_world():  
        print('Hello, World!')
        

def add(x, y):
        print("x is %s, y is %s" %(x, y))
        return x + y
        
        add(5, 6)    # => 11
        

def varargs(*args):
        return args
        
        varargs(1, 2, 3)  # => (1, 2, 3)
        

def keyword_args(**kwargs):
        return kwargs
        
        # => {"big": "foot", "loch": "ness"}
        keyword_args(big="foot", loch="ness")
        

def swap(x, y):
        return y, x
        
        x = 1
        y = 2
        x, y = swap(x, y)  # => x = 2, y = 1
        

def add(x, y=10):
        return x + y
        
        add(5)      # => 15
        add(5, 20)  # => 25
        

# => True
        (lambda x: x > 2)(3)
        
        # => 5
        (lambda x, y: x ** 2 + y ** 2)(2, 1)
        

import math
        print(math.sqrt(16))  # => 4.0
        

from math import ceil, floor
        print(ceil(3.7))   # => 4.0
        print(floor(3.7))  # => 3.0
        

from math import *
        

import math as m
        
        # => True
        math.sqrt(16) == m.sqrt(16)
        

import math
        dir(math)
        

#Line by line

with open("myfile.txt") as file:
        for line in file:
            print(line)
        

#With line number

file = open('myfile.txt', 'r')
        for i, line in enumerate(file, start=1):
        print("Number %s: %s" % (i, line))
        

#Write a string

contents = {"aa": 12, "bb": 21}
        with open("myfile1.txt", "w+") as file:
        file.write(str(contents))
        

#Read a string

with open('myfile1.txt', "r+") as file:
        contents = file.read()
        print(contents)
        

#Write an object

contents = {"aa": 12, "bb": 21}
        with open("myfile2.txt", "w+") as file:
        file.write(json.dumps(contents))
        

#Read an object

with open('myfile2.txt', "r+") as file:
        contents = json.load(file)
        print(contents)
        

import os
        os.remove("myfile.txt")
        

import os
        if os.path.exists("myfile.txt"):
        os.remove("myfile.txt")
        else:
        print("The file does not exist")
        

import os
        os.rmdir("myfolder")
        

class MyNewClass:
        pass
        
        # Class Instantiation
        my = MyNewClass()
        

class Animal:
        def __init__(self, voice):
            self.voice = voice
        
        cat = Animal('Meow')
        print(cat.voice)    # => Meow
        
        dog = Animal('Woof') 
        print(dog.voice)    # => Woof
        

class Dog:
        
        # Method of the class
        def bark(self):
            print("Ham-Ham")
        
        charlie = Dog()
        charlie.bark()   # => "Ham-Ham"
        

class Employee:
        def __init__(self, name):
            self.name = name
        
        def __repr__(self):
            return self.name
        
        Ram = Employee('Ram')
        print(Ram)  # => Ram
        

class CustomError(Exception):
        pass
        

class ParentClass:
        def print_self(self):
            print('A')
        
        class ChildClass(ParentClass):
        def print_self(self):
            print('B')
        
        obj_A = ParentClass()
        obj_B = ChildClass()
        
        obj_A.print_self() # => A
        obj_B.print_self() # => B
        

class ParentClass:
        def print_self(self):
            print("Parent")
        
        class ChildClass(ParentClass):
        def print_self(self):
            print("Child")
        
        child_instance = ChildClass()
        child_instance.print_self() # => Child
        

class Animal: 
        def __init__(self, name, legs):
            self.name = name
            self.legs = legs
            
        class Dog(Animal):
        def sound(self):
            print("Woof!")
        
        Yoki = Dog("Yoki", 4)
        print(Yoki.name) # => YOKI
        print(Yoki.legs) # => 4
        Yoki.sound()     # => Woof!
        

# This is a single line comments.
        

""" Multiline strings can be written
        using three "s, and are often used
        as documentation.
        """
        

''' Multiline strings can be written
        using three 's, and are often used
        as documentation.
        '''
        

def double_numbers(iterable):
        for i in iterable:
            yield i + i
        

Generators help you make lazy code.

values = (-x for x in [1,2,3,4,5])
        gen_to_list = list(values)
        
        # => [-1, -2, -3, -4, -5]
        print(gen_to_list)