Python Programming

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Syntax of Lambda Function in python

lambda arguments: expression

Example 1: Function to add 3 numbers

def adder(x,y,z):
    print("sum:",x+y+z)
adder(10,12,13)

Example 2: Using *args to pass the variable length arguments to the function

def adder(*num):
    sum = 0
    
    for n in num:
        sum = sum + n
    print("Sum:",sum)
adder(3,5)
adder(4,5,6,7)
adder(1,2,3,5,6)

Example 3: Using **kwargs to pass the variable keyword arguments to the function

def intro(**data):
    print("\nData type of argument:",type(data))
    for key, value in data.items():
        print("{} is {}".format(key,value))
intro(Firstname="Sita", Lastname="Sharma", Age=22, Phone=1234567890)
intro(Firstname="John", Lastname="Wood", Email="johnwood@nomail.com", Country="Wakanda", Age=25, Phone=9876543210)

Example 1: Using assert without Error Message

def avg(marks):
    assert len(marks) != 0
    return sum(marks)/len(marks)
mark1 = []
print("Average of mark1:",avg(mark1))

Example 2: Using assert with error message

def avg(marks):
    assert len(marks) != 0,"List is empty."
    return sum(marks)/len(marks)
mark2 = [55,88,78,90,79]
print("Average of mark2:",avg(mark2))
mark1 = []
print("Average of mark1:",avg(mark1))

Syntax of break

break

Example: Python break

# Use of break statement inside the loop
for val in "string":
    if val == "i":
        break
    print(val)
print("The end")

Syntax of Continue

continue

Example: Python continue

# Program to show the use of continue statement inside loops
for val in "string":
    if val == "i":
        continue
    print(val)
print("The end")

Example 1: Writing Single-Line Comments

# printing a string
print('Hello world')

Example 2: Using multiple #

# it is a
# multiline
# comment

Example 3: Using String Literals to write Multi-line Comments

'''
I am a
multiline comment!
'''
print("Hello World")

Example 1: Read CSV Having Comma Delimiter

import csv
with open('people.csv', 'r') as file:
    reader = csv.reader(file)
    for row in reader:
        print(row)

Example 2: Read CSV file Having Tab Delimiter

import csv
with open('people.csv', 'r',) as file:
    reader = csv.reader(file, delimiter = '\t')
    for row in reader:
        print(row)

Example 3: Write to a CSV file

import csv
with open('protagonist.csv', 'w', newline='') as file:
    writer = csv.writer(file)
    writer.writerow(["SN", "Movie", "Protagonist"])
    writer.writerow([1, "Lord of the Rings", "Frodo Baggins"])
    writer.writerow([2, "Harry Potter", "Harry Potter"])

Example 5: Writing to a CSV File with Tab Delimiter

import csv
with open('protagonist.csv', 'w') as file:
    writer = csv.writer(file, delimiter = '\t')
    writer.writerow(["SN", "Movie", "Protagonist"])
    writer.writerow([1, "Lord of the Rings", "Frodo Baggins"])
    writer.writerow([2, "Harry Potter", "Harry Potter"])

Example 7: Python csv.DictWriter()

import csv
with open('players.csv', 'w', newline='') as file:
    fieldnames = ['player_name', 'fide_rating']
    writer = csv.DictWriter(file, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'player_name': 'Magnus Carlsen', 'fide_rating': 2870})
    writer.writerow({'player_name': 'Fabiano Caruana', 'fide_rating': 2822})
    writer.writerow({'player_name': 'Ding Liren', 'fide_rating': 2801})

Example 2: Get Current Date


import datetime
date_object = datetime.date.today()
print(date_object)

Example 13: Printing negative timedelta object


from datetime import timedelta
t1 = timedelta(seconds = 33)
t2 = timedelta(seconds = 54)
t3 = t1 - t2
print("t3 =", t3)
print("t3 =", abs(t3))

Example 15: Format date using strftime()


from datetime import datetime
# current date and time
now = datetime.now()
t = now.strftime("%H:%M:%S")
print("time:", t)
s1 = now.strftime("%m/%d/%Y, %H:%M:%S")
# mm/dd/YY H:M:S format
print("s1:", s1)
s2 = now.strftime("%d/%m/%Y, %H:%M:%S")
# dd/mm/YY H:M:S format
print("s2:", s2)

Example 16: strptime()


from datetime import datetime
date_string = "21 June, 2018"
print("date_string =", date_string)
date_object = datetime.strptime(date_string, "%d %B, %Y")
print("date_object =", date_object)

Example 3: How to use Dictionary Comprehension

#item price in dollars
old_price = {'milk': 1.02, 'coffee': 2.5, 'bread': 2.5}
dollar_to_pound = 0.76
new_price = {item: value*dollar_to_pound for (item, value) in old_price.items()}
print(new_price)

Example 4: If Conditional Dictionary Comprehension

original_dict = {'jack': 38, 'michael': 48, 'guido': 57, 'john': 33}
even_dict = {k: v for (k, v) in original_dict.items() if v % 2 == 0}
print(even_dict)

Example 5: Multiple if Conditional Dictionary Comprehension

original_dict = {'jack': 38, 'michael': 48, 'guido': 57, 'john': 33}
new_dict = {k: v for (k, v) in original_dict.items() if v % 2 != 0 if v < 40}
print(new_dict)

Example 6: if-else Conditional Dictionary Comprehension

original_dict = {'jack': 38, 'michael': 48, 'guido': 57, 'john': 33}
new_dict_1 = {k: ('old' if v > 40 else 'young')
    for (k, v) in original_dict.items()}
print(new_dict_1)

Example 7: Nested Dictionary with Two Dictionary Comprehensions

dictionary = {
    k1: {k2: k1 * k2 for k2 in range(1, 6)} for k1 in range(2, 5)
}
print(dictionary)

Example 2: Printing docstring

def square(n):
    '''Takes in a number n, returns the square of n'''
    return n**2
print(square.__doc__)

Example 3: Docstrings for the built-in print() function

print(print.__doc__)

Example 4: Write single-line docstrings for a function

def multiplier(a, b):
    """Takes in two numbers, returns their product."""
    return a*b

Example 4: Docstrings of Python module

import pickle
print(pickle.__doc__)

Example 5: Docstrings for Python functions

def add_binary(a, b):
    '''
    Returns the sum of two decimal numbers in binary digits.
            Parameters:
                    a (int): A decimal integer
                    b (int): Another decimal integer
            Returns:
                    binary_sum (str): Binary string of the sum of a and b
    '''
    binary_sum = bin(a+b)[2:]
    return binary_sum
print(add_binary.__doc__)

Syntax of for Loop


for val in sequence:
    loop body

Example: Python for Loop

# Program to find the sum of all numbers stored in a list
# List of numbers
numbers = [6, 5, 3, 8, 4, 2, 5, 4, 11]
# variable to store the sum
sum = 0
# iterate over the list
for val in numbers:
    sum = sum+val
print("The sum is", sum)

Syntax of Function

def function_name(parameters):
	"""docstring"""
	statement(s)

Example of a function

def greet(name):
    """
    This function greets to
    the person passed in as
    a parameter
    """
    print("Hello, " + name + ". Good morning!")

Syntax of return

return [expression_list]

Example of return

def absolute_value(num):
    """This function returns the absolute
    value of the entered number"""
    if num >= 0:
        return num
    else:
        return -num
print(absolute_value(2))
print(absolute_value(-4))

Example 1: Create a Global Variable

x = "global"
def foo():
    print("x inside:", x)
foo()
print("x outside:", x)

Example 2: Accessing local variable outside the scope

def foo():
    y = "local"
foo()
print(y)

Example 4: Using Global and Local variables in the same code

x = "global "
def foo():
    global x
    y = "local"
    x = x * 2
    print(x)
    print(y)
foo()

Example 5: Global variable and Local variable with same name

x = 5
def foo():
    x = 10
    print("local x:", x)
foo()
print("global x:", x)

Example 6: Create a nonlocal variable

def outer():
    x = "local"
    def inner():
        nonlocal x
        x = "nonlocal"
        print("inner:", x)
    inner()
    print("outer:", x)
outer()

Python if Statement Syntax

if test expression:
    statement(s)

Example: Python if Statement

# If the number is positive, we print an appropriate message
num = 3
if num > 0:
    print(num, "is a positive number.")
print("This is always printed.")
num = -1
if num > 0:
    print(num, "is a positive number.")
print("This is also always printed.")

Syntax of if...else

if test expression:
    Body of if
else:
    Body of else

Example of if...else

# Program checks if the number is positive or negative
# And displays an appropriate message
num = 3
# Try these two variations as well. 
# num = -5
# num = 0
if num >= 0:
    print("Positive or Zero")
else:
    print("Negative number")

Syntax of if...elif...else

if test expression:
    Body of if
elif test expression:
    Body of elif
else: 
    Body of else

Example of if...elif...else

'''In this program, 
we check if the number is positive or
negative or zero and 
display an appropriate message'''
num = 3.4
# Try these two variations as well:
# num = 0
# num = -4.5
if num > 0:
    print("Positive number")
elif num == 0:
    print("Zero")
else:
    print("Negative number")

Python Nested if Example

'''In this program, we input a number
check if the number is positive or
negative or zero and display
an appropriate message
This time we use nested if statement'''
num = float(input("Enter a number: "))
if num >= 0:
    if num == 0:
        print("Zero")
    else:
        print("Positive number")
else:
    print("Negative number")

Python Inheritance Syntax

class BaseClass:
  Body of base class
class DerivedClass(BaseClass):
  Body of derived class

Example 3: Convert dict to JSON


import json
person_dict = {'name': 'Bob',
'age': 12,
'children': None
}
person_json = json.dumps(person_dict)
# Output: {"name": "Bob", "age": 12, "children": null}
print(person_json)

Example 4: Writing JSON to a file


import json
person_dict = {"name": "Bob",
"languages": ["English", "French"],
"married": True,
"age": 32
}
with open('person.txt', 'w') as json_file:
  json.dump(person_dict, json_file)

Example 5: Python pretty print JSON


import json
person_string = '{"name": "Bob", "languages": "English", "numbers": [2, 1.6, null]}'
# Getting dictionary
person_dict = json.loads(person_string)
# Pretty Printing JSON string back
print(json.dumps(person_dict, indent = 4, sort_keys=True))

Example 2: Iterating through a string Using List Comprehension

h_letters = [ letter for letter in 'human' ]
print( h_letters)

Syntax of List Comprehension

[expression for item in list]

Example #1: Infinite loop using while

# An example of infinite loop
# press Ctrl + c to exit from the loop
while True:
   num = int(input("Enter an integer: "))
   print("The double of",num,"is",2 * num)

Example #2: Loop with condition at the top


# Program to illustrate a loop with the condition at the top
# Try different numbers
n = 10
# Uncomment to get user input
#n = int(input("Enter n: "))
# initialize sum and counter
sum = 0
i = 1
while i <= n:
   sum = sum + i
   i = i+1    # update counter
# print the sum
print("The sum is",sum)

Example #3: Loop with condition in the middle

# Program to illustrate a loop with condition in the middle. 
# Take input from the user until a vowel is entered
vowels = "aeiouAEIOU"
# infinite loop
while True:
   v = input("Enter a vowel: ")
   # condition in the middle
   if v in vowels:
       break
   print("That is not a vowel. Try again!")
print("Thank you!")

Example #4: Loop with condition at the bottom


# Python program to illustrate a loop with the condition at the bottom
# Roll a dice until the user chooses to exit
# import random module
import random
while True:
   input("Press enter to roll the dice")
   # get a number between 1 to 6
   num = random.randint(1,6)
   print("You got",num)
   option = input("Roll again?(y/n) ")
   # condition
   if option == 'n':
       break

class Base1:
    pass
class Base2:
    pass
class MultiDerived(Base1, Base2):
    pass

Example 1: How to create a nested dictionary

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'}}
print(people)

Example 2: Access the elements using the [] syntax

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'}}
print(people[1]['name'])
print(people[1]['age'])
print(people[1]['sex'])

Example 3: How to change or add elements in a nested dictionary?

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'}}
people[3] = {}
people[3]['name'] = 'Luna'
people[3]['age'] = '24'
people[3]['sex'] = 'Female'
people[3]['married'] = 'No'
print(people[3])

Example 4: Add another dictionary to the nested dictionary

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'},
          3: {'name': 'Luna', 'age': '24', 'sex': 'Female', 'married': 'No'}}
people[4] = {'name': 'Peter', 'age': '29', 'sex': 'Male', 'married': 'Yes'}
print(people[4])

Example 5: How to delete elements from a nested dictionary?

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'},
          3: {'name': 'Luna', 'age': '24', 'sex': 'Female', 'married': 'No'},
          4: {'name': 'Peter', 'age': '29', 'sex': 'Male', 'married': 'Yes'}}
del people[3]['married']
del people[4]['married']
print(people[3])
print(people[4])

Example 6: How to delete dictionary from a nested dictionary?

people = {1: {'name': 'John', 'age': '27', 'sex': 'Male'},
          2: {'name': 'Marie', 'age': '22', 'sex': 'Female'},
          3: {'name': 'Luna', 'age': '24', 'sex': 'Female'},
          4: {'name': 'Peter', 'age': '29', 'sex': 'Male'}}
del people[3], people[4]
print(people)

Example 7: How to iterate through a Nested dictionary?

people = {1: {'Name': 'John', 'Age': '27', 'Sex': 'Male'},
          2: {'Name': 'Marie', 'Age': '22', 'Sex': 'Female'}}
for p_id, p_info in people.items():
    print("\nPerson ID:", p_id)
    
    for key in p_info:
        print(key + ':', p_info[key])

Example 1: Creating Class and Object in Python

class Parrot:
    # class attribute
    species = "bird"
    # instance attribute
    def __init__(self, name, age):
        self.name = name
        self.age = age
# instantiate the Parrot class
blu = Parrot("Blu", 10)
woo = Parrot("Woo", 15)
# access the class attributes
print("Blu is a {}".format(blu.__class__.species))
print("Woo is also a {}".format(woo.__class__.species))
# access the instance attributes
print("{} is {} years old".format( blu.name, blu.age))
print("{} is {} years old".format( woo.name, woo.age))

Example 2 : Creating Methods in Python

class Parrot:
    
    # instance attributes
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    # instance method
    def sing(self, song):
        return "{} sings {}".format(self.name, song)
    def dance(self):
        return "{} is now dancing".format(self.name)
# instantiate the object
blu = Parrot("Blu", 10)
# call our instance methods
print(blu.sing("'Happy'"))
print(blu.dance())

Example 3: Use of Inheritance in Python

# parent class
class Bird:
    
    def __init__(self):
        print("Bird is ready")
    def whoisThis(self):
        print("Bird")
    def swim(self):
        print("Swim faster")
# child class
class Penguin(Bird):
    def __init__(self):
        # call super() function
        super().__init__()
        print("Penguin is ready")
    def whoisThis(self):
        print("Penguin")
    def run(self):
        print("Run faster")
peggy = Penguin()
peggy.whoisThis()
peggy.swim()
peggy.run()

Example 4: Data Encapsulation in Python

class Computer:
    def __init__(self):
        self.__maxprice = 900
    def sell(self):
        print("Selling Price: {}".format(self.__maxprice))
    def setMaxPrice(self, price):
        self.__maxprice = price
c = Computer()
c.sell()
# change the price
c.__maxprice = 1000
c.sell()
# using setter function
c.setMaxPrice(1000)
c.sell()

Example 5: Using Polymorphism in Python

class Parrot:
    def fly(self):
        print("Parrot can fly")
    
    def swim(self):
        print("Parrot can't swim")
class Penguin:
    def fly(self):
        print("Penguin can't fly")
    
    def swim(self):
        print("Penguin can swim")
# common interface
def flying_test(bird):
    bird.fly()
#instantiate objects
blu = Parrot()
peggy = Penguin()
# passing the object
flying_test(blu)
flying_test(peggy)

Example 1: Arithmetic operators in Python

x = 15
y = 4
# Output: x + y = 19
print('x + y =',x+y)
# Output: x - y = 11
print('x - y =',x-y)
# Output: x * y = 60
print('x * y =',x*y)
# Output: x / y = 3.75
print('x / y =',x/y)
# Output: x // y = 3
print('x // y =',x//y)
# Output: x ** y = 50625
print('x ** y =',x**y)

Example 2: Comparison operators in Python

x = 10
y = 12
# Output: x > y is False
print('x > y is',x>y)
# Output: x < y is True
print('x < y is',x<y)
# Output: x == y is False
print('x == y is',x==y)
# Output: x != y is True
print('x != y is',x!=y)
# Output: x >= y is False
print('x >= y is',x>=y)
# Output: x <= y is True
print('x <= y is',x<=y)

Example 3: Logical Operators in Python

x = True
y = False
print('x and y is',x and y)
print('x or y is',x or y)
print('not x is',not x)

Example 4: Identity operators in Python

x1 = 5
y1 = 5
x2 = 'Hello'
y2 = 'Hello'
x3 = [1,2,3]
y3 = [1,2,3]
# Output: False
print(x1 is not y1)
# Output: True
print(x2 is y2)
# Output: False
print(x3 is y3)

Example #5: Membership operators in Python

x = 'Hello world'
y = {1:'a',2:'b'}
# Output: True
print('H' in x)
# Output: True
print('hello' not in x)
# Output: True
print(1 in y)
# Output: False
print('a' in y)

Syntax of pass

pass

Example: pass Statement

'''pass is just a placeholder for
functionality to be added later.'''
sequence = {'p', 'a', 's', 's'}
for val in sequence:
    pass

Example 2: Polymorphic len() function

print(len("Programiz"))
print(len(["Python", "Java", "C"]))
print(len({"Name": "John", "Address": "Nepal"}))

Example 3: Polymorphism in Class Methods

class Cat:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def info(self):
        print(f"I am a cat. My name is {self.name}. I am {self.age} years old.")
    def make_sound(self):
        print("Meow")
class Dog:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def info(self):
        print(f"I am a dog. My name is {self.name}. I am {self.age} years old.")
    def make_sound(self):
        print("Bark")
cat1 = Cat("Kitty", 2.5)
dog1 = Dog("Fluffy", 4)
for animal in (cat1, dog1):
    animal.make_sound()
    animal.info()
    animal.make_sound()

Example 4: Method Overriding

from math import pi
class Shape:
    def __init__(self, name):
        self.name = name
    def area(self):
        pass
    def fact(self):
        return "I am a two-dimensional shape."
    def __str__(self):
        return self.name
class Square(Shape):
    def __init__(self, length):
        super().__init__("Square")
        self.length = length
    def area(self):
        return self.length**2
    def fact(self):
        return "Squares have each angle equal to 90 degrees."
class Circle(Shape):
    def __init__(self, radius):
        super().__init__("Circle")
        self.radius = radius
    def area(self):
        return pi*self.radius**2
a = Square(4)
b = Circle(7)
print(b)
print(b.fact())
print(a.fact())
print(b.area())

Example 2: Read CSV file Having Tab Delimiter

import csv
with open('innovators.csv', 'r') as file:
    reader = csv.reader(file, delimiter = '\t')
    for row in reader:
        print(row)

Example 4: Read CSV files with quotes

import csv
with open('person1.csv', 'r') as file:
    reader = csv.reader(file, quoting=csv.QUOTE_ALL, skipinitialspace=True)
    for row in reader:
        print(row)

Example of a recursive function

def factorial(x):
    """This is a recursive function
    to find the factorial of an integer"""
    if x == 1:
        return 1
    else:
        return (x * factorial(x-1))
num = 3
print("The factorial of", num, "is", factorial(num))

Example 1: re.findall()


# Program to extract numbers from a string
import re
string = 'hello 12 hi 89. Howdy 34'
pattern = '\d+'
result = re.findall(pattern, string) 
print(result)
# Output: ['12', '89', '34']

Example 2: re.split()


import re
string = 'Twelve:12 Eighty nine:89.'
pattern = '\d+'
result = re.split(pattern, string) 
print(result)
# Output: ['Twelve:', ' Eighty nine:', '.']

Example 3: re.sub()


# Program to remove all whitespaces
import re
# multiline string
string = 'abc 12\
de 23 \n f45 6'
# matches all whitespace characters
pattern = '\s+'
# empty string
replace = ''
new_string = re.sub(pattern, replace, string) 
print(new_string)
# Output: abc12de23f456

Example 4: re.subn()


# Program to remove all whitespaces
import re
# multiline string
string = 'abc 12\
de 23 \n f45 6'
# matches all whitespace characters
pattern = '\s+'
# empty string
replace = ''
new_string = re.subn(pattern, replace, string) 
print(new_string)
# Output: ('abc12de23f456', 4)

Example 5: re.search()


import re
string = "Python is fun"
# check if 'Python' is at the beginning
match = re.search('\APython', string)
if match:
  print("pattern found inside the string")
else:
  print("pattern not found")  
# Output: pattern found inside the string

Example 6: Match object


import re
string = '39801 356, 2102 1111'
# Three digit number followed by space followed by two digit number
pattern = '(\d{3}) (\d{2})'
# match variable contains a Match object.
match = re.search(pattern, string) 
if match:
  print(match.group())
else:
  print("pattern not found")
# Output: 801 35

Example 7: Raw string using r prefix


import re
string = '\n and \r are escape sequences.'
result = re.findall(r'[\n\r]', string) 
print(result)
# Output: ['\n', '\r']

Example 1: Copy using = operator

old_list = [[1, 2, 3], [4, 5, 6], [7, 8, 'a']]
new_list = old_list
new_list[2][2] = 9
print('Old List:', old_list)
print('ID of Old List:', id(old_list))
print('New List:', new_list)
print('ID of New List:', id(new_list))

Example 2: Create a copy using shallow copy

import copy
old_list = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
new_list = copy.copy(old_list)
print("Old list:", old_list)
print("New list:", new_list)

Example 3: Adding [4, 4, 4] to old_list, using shallow copy

import copy
old_list = [[1, 1, 1], [2, 2, 2], [3, 3, 3]]
new_list = copy.copy(old_list)
old_list.append([4, 4, 4])
print("Old list:", old_list)
print("New list:", new_list)

Example 4: Adding new nested object using Shallow copy

import copy
old_list = [[1, 1, 1], [2, 2, 2], [3, 3, 3]]
new_list = copy.copy(old_list)
old_list[1][1] = 'AA'
print("Old list:", old_list)
print("New list:", new_list)

Example 5: Copying a list using deepcopy()

import copy
old_list = [[1, 1, 1], [2, 2, 2], [3, 3, 3]]
new_list = copy.deepcopy(old_list)
print("Old list:", old_list)
print("New list:", new_list)

Example 6: Adding a new nested object in the list using Deep copy

import copy
old_list = [[1, 1, 1], [2, 2, 2], [3, 3, 3]]
new_list = copy.deepcopy(old_list)
old_list[1][0] = 'BB'
print("Old list:", old_list)
print("New list:", new_list)

"Hello, World!" Program

print("Hello, World!")

How to define a class?

class MyClass:
   a = 10
   def func(self):
      print('Hello')

Example 1: Converting integer to float

num_int = 123
num_flo = 1.23
num_new = num_int + num_flo
print("datatype of num_int:",type(num_int))
print("datatype of num_flo:",type(num_flo))
print("Value of num_new:",num_new)
print("datatype of num_new:",type(num_new))

Example 2: Addition of string(higher) data type and integer(lower) datatype

num_int = 123
num_str = "456"
print("Data type of num_int:",type(num_int))
print("Data type of num_str:",type(num_str))
print(num_int+num_str)

Example 3: Addition of string and integer using explicit conversion

num_int = 123
num_str = "456"
print("Data type of num_int:",type(num_int))
print("Data type of num_str before Type Casting:",type(num_str))
num_str = int(num_str)
print("Data type of num_str after Type Casting:",type(num_str))
num_sum = num_int + num_str
print("Sum of num_int and num_str:",num_sum)
print("Data type of the sum:",type(num_sum))

Example 1: Declaring and assigning value to a variable

website = "apple.com"
print(website)

Example 2: Changing the value of a variable

website = "apple.com"
print(website)
# assigning a new value to website
website = "programiz.com"
print(website)

Example 3: Assigning multiple values to multiple variables

a, b, c = 5, 3.2, "Hello"
print (a)
print (b)
print (c)

Example 4: How to use Numeric literals in Python?

a = 0b1010 #Binary Literals
b = 100 #Decimal Literal 
c = 0o310 #Octal Literal
d = 0x12c #Hexadecimal Literal
#Float Literal
float_1 = 10.5 
float_2 = 1.5e2
#Complex Literal 
x = 3.14j
print(a, b, c, d)
print(float_1, float_2)
print(x, x.imag, x.real)

Example 7: How to use string literals in Python?

strings = "This is Python"
char = "C"
multiline_str = """This is a multiline string with more than one line code."""
unicode = u"\u00dcnic\u00f6de"
raw_str = r"raw \n string"
print(strings)
print(char)
print(multiline_str)
print(unicode)
print(raw_str)

Example 8: How to use boolean literals in Python?

x = (1 == True)
y = (1 == False)
a = True + 4
b = False + 10
print("x is", x)
print("y is", y)
print("a:", a)
print("b:", b)

Example 9: How to use special literals in Python?

drink = "Available"
food = None
def menu(x):
    if x == drink:
        print(drink)
    else:
        print(food)
menu(drink)
menu(food)

Example 10: How to use literals collections in Python?

fruits = ["apple", "mango", "orange"] #list
numbers = (1, 2, 3) #tuple
alphabets = {'a':'apple', 'b':'ball', 'c':'cat'} #dictionary
vowels = {'a', 'e', 'i' , 'o', 'u'} #set
print(fruits)
print(numbers)
print(alphabets)
print(vowels)

Syntax of while Loop in Python

while test_expression:
    Body of while

Example: Python while Loop

# Program to add natural
# numbers up to 
# sum = 1+2+3+...+n
# To take input from the user,
# n = int(input("Enter n: "))
n = 10
# initialize sum and counter
sum = 0
i = 1
while i <= n:
    sum = sum + i
    i = i+1    # update counter
# print the sum
print("The sum is", sum)

Example 3: Write CSV File Having Pipe Delimiter

import csv
data_list = [["SN", "Name", "Contribution"],
             [1, "Linus Torvalds", "Linux Kernel"],
             [2, "Tim Berners-Lee", "World Wide Web"],
             [3, "Guido van Rossum", "Python Programming"]]
with open('innovators.csv', 'w', newline='') as file:
    writer = csv.writer(file, delimiter='|')
    writer.writerows(data_list)

Example 4: Write CSV files with quotes

import csv
row_list = [
    ["SN", "Name", "Quotes"],
    [1, "Buddha", "What we think we become"],
    [2, "Mark Twain", "Never regret anything that made you smile"],
    [3, "Oscar Wilde", "Be yourself everyone else is already taken"]
]
with open('quotes.csv', 'w', newline='') as file:
    writer = csv.writer(file, quoting=csv.QUOTE_NONNUMERIC, delimiter=';')
    writer.writerows(row_list)

Example 5: Writing CSV files with custom quoting character

import csv
row_list = [
    ["SN", "Name", "Quotes"],
    [1, "Buddha", "What we think we become"],
    [2, "Mark Twain", "Never regret anything that made you smile"],
    [3, "Oscar Wilde", "Be yourself everyone else is already taken"]
]
with open('quotes.csv', 'w', newline='') as file:
    writer = csv.writer(file, quoting=csv.QUOTE_NONNUMERIC,
                        delimiter=';', quotechar='*')
    writer.writerows(row_list)

Example 7: Python csv.DictWriter()

import csv
with open('players.csv', 'w', newline='') as file:
    fieldnames = ['player_name', 'fide_rating']
    writer = csv.DictWriter(file, fieldnames=fieldnames)
    writer.writeheader()
    writer.writerow({'player_name': 'Magnus Carlsen', 'fide_rating': 2870})
    writer.writerow({'player_name': 'Fabiano Caruana', 'fide_rating': 2822})
    writer.writerow({'player_name': 'Ding Liren', 'fide_rating': 2801})

Example 8: Using escapechar in csv writer

import csv
row_list = [
    ['Book', 'Quote'],
    ['Lord of the Rings',
        '"All we have to decide is what to do with the time that is given us."'],
    ['Harry Potter', '"It matters not what someone is born, but what they grow to be."']
]
with open('book.csv', 'w', newline='') as file:
    writer = csv.writer(file, escapechar='/', quoting=csv.QUOTE_NONE)
    writer.writerows(row_list)

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Python Programming

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