How to Learn Python from Scratch in 2025 (original) (raw)

Python is a general-purpose high-level programming language and is widely used among the developers’ community. Python was mainly developed with an emphasis on code readability, and its syntax allows programmers to express concepts in fewer lines of code.

Learn Python from Scratch

If you are new to programming and want to learn Python Programming from Scratch, then this complete 2024 Python course guide is here to help you. Whether you are an experienced programmer or new to the programming world, this guide will help you with the knowledge and resources needed to get started with Python Language.

Key features of Python

Python has many reasons for being popular and in demand. A few of the reasons are mentioned below.

Application Areas

python-applications

Getting started with Python Programming –

Python is a lot easier to code and learn. Python programs can be written on any plain text editor like notepad, notepad++, or anything of that sort. One can also use an online IDE for writing Python codes or can even install one on their system to make it more feasible to write these codes because IDEs provide a lot of features like intuitive code editor, debugger, compiler, etc.
To begin with, writing Python Codes and performing various intriguing and useful operations, one must have Python installed on their System. This can be done by following the step by step instructions provided below:

What if Python already exists? Let’s check

Windows don’t come with Python preinstalled, it needs to be installed explicitly. But unlike windows, most of the Linux OS have Python pre-installed, also macOS comes with Python pre-installed.
To check if your device is pre-installed with Python or not, just go to **Command Line(For **Windows, search for **cmd in the Run dialog( + **R), for **Linux open the terminal using Ctrl+Alt+T, for **macOS use
control+Option+Shift+T.

Now run the following command:

**For Python2

python --version

**For Python3

python3 --version

If Python is already installed, it will generate a message with the Python version available.

learn python

Download and Installation

Before starting with the installation process, you need to download it. For that all versions of Python for Windows, Linux, and MacOS are available on python.org.

How-to-install-Python-for-windows-11

Download the Python and follow the further instructions for the installation of Python.

**Beginning the installation.

How to run a Python program

Let’s consider a simple Hello World Program.

Python `

Python program to print

Hello World

print("Hello World")

`

Generally, there are two ways to run a Python program.

Windows

Open Commandline and then to compile the code type **python HelloWorld.py. If your code has no error then it will execute properly and output will be displayed.

python-hellow-world-windows

Unix/Linux

Open Terminal of your Unix/Linux OS and then to compile the code type **python HelloWorld.py. If your code has no error then it will execute properly and output will be displayed.

python-linux-hello-world

Fundamentals of Python

Python Indentation

Python uses indentation to highlight the blocks of code. Whitespace is used for indentation in Python. All statements with the same distance to the right belong to the same block of code. If a block has to be more deeply nested, it is simply indented further to the right. You can understand it better by looking at the following lines of code.

Python `

Python program showing

indentation

site = 'gfg'

if site == 'gfg': print('Logging on to geeksforgeeks...') else: print('retype the URL.') print('All set !')

`

Output

Logging on to geeksforgeeks... All set !

The lines print(‘Logging on to geeksforgeeks…’) and print(‘retype the URL.’) are two separate code blocks. The two blocks of code in our example if-statement are both indented four spaces. The final print(‘All set!’) is not indented, and so it does not belong to the else-block.

Comments are useful information that the developers provide to make the reader understand the source code. It explains the logic or a part of it used in the code. There are two types of comment in Python:

**Single line comments: Python single line comment starts with hashtag symbol with no white spaces.

Python `

This is a comment

Print “GeeksforGeeks !” to console

print("GeeksforGeeks")

`

**Multi-line string as comment: Python multi-line comment is a piece of text enclosed in a delimiter (“””) on each end of the comment.

Python `

""" This would be a multiline comment in Python that spans several lines and describes geeksforgeeks. A Computer Science portal for geeks. It contains
well written, well thought
and well-explained computer science
and programming articles,
quizzes and more.
… """ print("GeeksForGeeks")

`

**Note: For more information, refer Comments in Python.

Variables

Variables in Python are not “statically typed”. We do not need to declare variables before using them or declare their type. A variable is created the moment we first assign a value to it.

Python `

#!/usr/bin/python

An integer assignment

age = 45

A floating point

salary = 1456.8

A string

name = "John"

print(age) print(salary) print(name)

`

Operators

Operators are the main building block of any programming language. Operators allow the programmer to perform different kinds of operations on operands. These operators can be categorized based upon their different functionality:

**Arithmetic operators: Arithmetic operators are used to perform mathematical operations like addition, subtraction, multiplication and division.

Python `

Examples of Arithmetic Operator

a = 9 b = 4

Addition of numbers

add = a + b

Subtraction of numbers

sub = a - b

Multiplication of number

mul = a * b

Division(float) of number

div1 = a / b

Division(floor) of number

div2 = a // b

Modulo of both number

mod = a % b

print results

print(add) print(sub) print(mul) print(div1) print(div2) print(mod)

`

**Relational Operators: Relational operators compares the values. It either returns True or False according to the condition.

Python `

Examples of Relational Operators

a = 13 b = 33

a > b is False

print(a > b)

a < b is True

print(a < b)

a == b is False

print(a == b)

a != b is True

print(a != b)

a >= b is False

print(a >= b)

a <= b is True

print(a <= b)

`

Output

False True False True False True

**Logical Operators: Logical operators perform Logical AND, Logical OR and Logical NOT operations.

Python `

Examples of Logical Operator

a = True b = False

Print a and b is False

print(a and b)

Print a or b is True

print(a or b)

Print not a is False

print(not a)

`

**Output:

False
True
False

**Bitwise operators: Bitwise operator acts on bits and performs bit by bit operation.

Python `

Examples of Bitwise operators

a = 10 b = 4

Print bitwise AND operation

print(a & b)

Print bitwise OR operation

print(a | b)

Print bitwise NOT operation

print(~a)

print bitwise XOR operation

print(a ^ b)

print bitwise right shift operation

print(a >> 2)

print bitwise left shift operation

print(a << 2)

`

**Output:

0
14
-11
14
2
40

**Assignment operators: Assignment operators are used to assign values to the variables.

**Special operators: Special operators are of two types-

Examples of Identity and

Membership operator

a1 = 'GeeksforGeeks' b1 = 'GeeksforGeeks'

Identity operator

print(a1 is not b1) print(a1 is b1)

Membership operator

print("G" in a1) print("N" not in b1)

`

**Output:

False
True
True
True

Basics of Input/Output

Taking input from user –

Python provides us with two inbuilt functions to read the input from the keyboard.

Python program showing

a use of raw_input()

g = raw_input("Enter your name : ") print g

`

Python program showing

a use of input()

val = input("Enter your value: ") print(val)

`

**Note: For more information, refer Python input() and raw_input().

Printing output to console –

The simplest way to produce output is using the print() function where you can pass zero or more expressions separated by commas. This function converts the expressions you pass into a string before writing to the screen.

Python `

Python 3.x program showing

how to print data on

a screen

One object is passed

print("GeeksForGeeks")

x = 5

Two objects are passed

print("x =", x)

code for disabling the softspace feature

print('G', 'F', 'G', sep ='')

using end argument

print("Python", end = '@')
print("GeeksforGeeks")

`

**Output:

GeeksForGeeks
x = 5
GFG
Python@GeeksforGeeks

Data Types

Data types are the classification or categorization of data items. It represents the kind of value that tells what operations can be performed on a particular data. Since everything is an object in Python programming, data types are actually classes and variables are instance (object) of these classes.

Python-data-structure

Numeric

In Python, numeric data type represent the data which has numeric value. Numeric value can be interger, floating number or even complex numbers. These values are defined as int, float and complex class in Python.

Python `

Python program to

demonstrate numeric value

print("Type of a: ", type(5))

print("\nType of b: ", type(5.0))

c = 2 + 4j print("\nType of c: ", type(c))

`

**Output:

Type of a: <class 'int'>

Type of b: <class 'float'>

Type of c: <class 'complex'>

Sequence Type

In Python, a sequence is the ordered collection of similar or different data types. Sequences allow storing multiple values in an organized and efficient fashion. There are several sequence types in Python –

**1) String: A string is a collection of one or more characters put in a single quote, double-quote or triple quote. In python there is no character data type, a character is a string of length one. It is represented by str class. Strings in Python can be created using single quotes or double quotes or even triple quotes.

Python `

Python Program for

Creation of String

String with single quotes

print('Welcome to the Geeks World')

String with double quotes

print("I'm a Geek")

String with triple quotes

print('''I'm a Geek and I live in a world of "Geeks"''')

`

**Output:

Welcome to the Geeks World
I'm a Geek
I'm a Geek and I live in a world of "Geeks"

**Accessing elements of string –

strings

Python `

Python Program to Access

characters of String

String1 = "GeeksForGeeks"

Printing First character

print(String1[0])

Printing Last character

print(String1[-1])

`

**Output:

G
s

**Deleting/Updating from a String –

In Python, Updation or deletion of characters from a String is not allowed because Strings are immutable. Only new strings can be reassigned to the same name.

Python `

Python Program to Update / delete

character of a String

String1 = "Hello, I'm a Geek"

Updating a character

String1[2] = 'p'

Deleting a character

del String1[2]

`

**Output:

Traceback (most recent call last):
File “/home/360bb1830c83a918fc78aa8979195653.py”, line 6, in
String1[2] = ‘p’
TypeError: ‘str’ object does not support item assignment

Traceback (most recent call last):
File “/home/499e96a61e19944e7e45b7a6e1276742.py”, line 8, in
del String1[2]
TypeError: ‘str’ object doesn’t support item deletion

**Note: For more information, refer Python String.

**Refer to the below articles to know more about Strings:

**2) List: Lists are just like the arrays, declared in other languages. A single list may contain DataTypes like Integers, Strings, as well as Objects. The elements in a list are indexed according to a definite sequence and the indexing of a list is done with 0 being the first index. It is represented by list class.

Python `

Python program to demonstrate

Creation of List

Creating a List

List = []
print(List)

Creating a list of strings

List = ['GeeksForGeeks', 'Geeks'] print(List)

Creating a Multi-Dimensional List

List = [['Geeks', 'For'], ['Geeks']]
print(List)

`

**Output:

[]
['GeeksForGeeks', 'Geeks']
[['Geeks', 'For'], ['Geeks']]

**Adding Elements to a List: Using append(), insert() and extend()

Python `

Python program to demonstrate

Addition of elements in a List

Creating a List

List = []

Using append()

List.append(1)
List.append(2) print(List)

Using insert()

List.insert(3, 12)
List.insert(0, 'Geeks') print(List)

Using extend()

List.extend([8, 'Geeks', 'Always'])
print(List)

`

**Output:

[1, 2]
['Geeks', 1, 2, 12]
['Geeks', 1, 2, 12, 8, 'Geeks', 'Always']

**Accessing elements from the List –

Use the index operator [ ] to access an item in a list. In Python, negative sequence indexes represent positions from the end of the array. Instead of having to compute the offset as in List[len(List)-3], it is enough to just write List[-3].

Python `

Python program to demonstrate

accessing of element from list

List = [1, 2, 3, 4, 5, 6]

accessing a element

print(List[0])
print(List[2])

Negative indexing

print the last element of list

print(List[-1])

print the third last element of list

print(List[-3])

`

**Output:

1
3
6
4

**Removing Elements from the List: Using remove() and pop()

Python `

Python program to demonstrate

Removal of elements in a List

Creating a List

List = [1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12]

using Remove() method

List.remove(5)
List.remove(6) print(List)

using pop()

List.pop() print(List)

`

**Output:

[1, 2, 3, 4, 7, 8, 9, 10, 11, 12]
[1, 2, 3, 4, 7, 8, 9, 10, 11]

**Note: For more information, refer Python List.

**Refer to the below articles to know more about List:

**3) Tuple: Tuple is an ordered collection of Python objects much like a list. The important difference between a list and a tuple is that tuples are immutable. It is represented by tuple class. In Python, tuples are created by placing a sequence of values separated by ‘comma’ with or without the use of parentheses for grouping of the data sequence.

Python `

Python program to demonstrate

creation of Set

Creating an empty tuple

Tuple1 = () print (Tuple1)

Creating a tuple of strings

print(('Geeks', 'For'))

Creating a Tuple of list

print(tuple([1, 2, 4, 5, 6]))

Creating a nested Tuple

Tuple1 = (0, 1, 2, 3)
Tuple2 = ('python', 'geek')
Tuple3 = (Tuple1, Tuple2) print(Tuple3)

`

**Output:

()
('Geeks', 'For')
(1, 2, 4, 5, 6)
((0, 1, 2, 3), ('python', 'geek'))

**Accessing element of a tuple –

Use the index operator [ ] to access an item in a tuple.

Python `

Python program to

demonstrate accessing tuple

tuple1 = tuple([1, 2, 3, 4, 5])

Accessing element using indexing

print(tuple1[0])

Accessing element using Negative

Indexing

print(tuple1[-1])

`

**Output:

1
5

**Deleting/updating elements of tuple –

Items of a tuple cannot be deleted as tuples are immutable in Python. Only new tuples can be reassigned to the same name.

Python `

Python program to

demonstrate updation / deletion

from a tuple

tuple1 = tuple([1, 2, 3, 4, 5])

Updating an element

tuple1[0] = -1

Deleting an element

del tuple1[2]

`

**Output:

Traceback (most recent call last):
File "/home/084519a8889e9b0103b874bbbb93e1fb.py", line 11, in
tuple1[0] = -1
TypeError: 'tuple' object does not support item assignment

Traceback (most recent call last):
File "/home/ffb3f8be85dd393bde5d0483ff191343.py", line 12, in
del tuple1[2]
TypeError: 'tuple' object doesn't support item deletion

**Note: For more information, refer Python Tuples.

**Refer to the below articles to know more about tuples:

Boolean

Booleans are data type with one of the two built-in values, True or False. It is denoted by the class bool.

Python `

Python program to

demonstrate boolean type

print(type(True)) print(1>2) print('a'=='a')

`

**Output:

<class 'bool'>
False
True

Set

In Python, Set is an unordered collection of data type that is iterable, mutable and has no duplicate elements. The order of elements in a set is undefined though it may consist of various elements. Sets can be created by using the built-in set() function with an iterable object or a sequence by placing the sequence inside curly braces {}, separated by ‘comma’.

Python `

Python program to demonstrate

Creation of Set in Python

Creating a Set

set1 = set()

Creating a Set of String

set1 = set("GeeksForGeeks") print(set1)

Creating a Set of List

set1 = set(["Geeks", "For", "Geeks"]) print(set1)

`

**Output:

{'o', 'r', 'k', 'G', 'e', 's', 'F'}
{'Geeks', 'For'}

**Adding elements: Using add() and update()

Python `

Python program to demonstrate

Addition of elements in a Set

set1 = set()

Adding to the Set using add()

set1.add(8) set1.add((6, 7)) print(set1)

Additio to the Set using Update()

set1.update([10, 11]) print(set1)

`

**Output:

{8, (6, 7)}
{8, 10, 11, (6, 7)}

**Accessing a Set: One can loop through the set items using a for loop as set items cannot be accessed by referring to an index.

Python `

Python program to demonstrate

Accessing of elements in a set

Creating a set

set1 = set(["Geeks", "For", "Geeks"])

Accessing using for loop

for i in set1:
print(i, end =" ")

`

**Output:

Geeks For

**Removing elements from a set: Using remove(), discard(), pop() and clear()

Python `

Python program to demonstrate

Deletion of elements in a Set

set1 = set([1, 2, 3, 4, 5, 6,
7, 8, 9, 10, 11, 12])

using Remove() method

set1.remove(5)
set1.remove(6) print(set1)

using Discard() method

set1.discard(8)
set1.discard(9) print(set1)

Set using the pop() method

set1.pop() print(set1)

Set using clear() method

set1.clear() print(set1)

`

**Output:

{1, 2, 3, 4, 7, 8, 9, 10, 11, 12}
{1, 2, 3, 4, 7, 10, 11, 12}
{2, 3, 4, 7, 10, 11, 12}
set()

**Note: For more information, refer Python Sets.

**Refer to the below articles to know more about Sets:

Dictionary

Dictionary in Python is an unordered collection of data values, used to store data values like a map. Dictionary holds key:value pair. Each key-value pair in a Dictionary is separated by a colon :, whereas each key is separated by a ‘comma’. A Dictionary can be created by placing a sequence of elements within curly {} braces, separated by ‘comma’.

Python `

Creating an empty Dictionary

Dict = {} print(Dict)

with Integer Keys

Dict = {1: 'Geeks', 2: 'For', 3: 'Geeks'} print(Dict)

with Mixed keys

Dict = {'Name': 'Geeks', 1: [1, 2, 3, 4]} print(Dict)

`

**Output:

{}
{1: 'Geeks', 2: 'For', 3: 'Geeks'}
{1: [1, 2, 3, 4], 'Name': 'Geeks'}

**Nested Dictionary:

Nested-Dictionary

Python `

Creating a Nested Dictionary

as shown in the below image

Dict = {1: 'Geeks', 2: 'For',
3:{'A' : 'Welcome', 'B' : 'To', 'C' : 'Geeks'}}

print(Dict)

`

**Output:

{1: 'Geeks', 2: 'For', 3: {'A': 'Welcome', 'B': 'To', 'C': 'Geeks'}}

**Note: For more information, refer Python Nested Dictionary.
**Adding elements to a Dictionary: One value at a time can be added to a Dictionary by defining value along with the key e.g. Dict[Key] = ‘Value’.

Python `

Creating an empty Dictionary

Dict = {}

Adding elements one at a time

Dict[0] = 'Geeks' Dict[2] = 'For' Dict[3] = 1 print(Dict)

Updating existing Key's Value

Dict[2] = 'Welcome' print(Dict)

`

**Output:

{0: 'Geeks', 2: 'For', 3: 1}
{0: 'Geeks', 2: 'Welcome', 3: 1}

**Accessing elements from a Dictionary: In order to access the items of a dictionary refer to its key name or use get() method.

Python `

Python program to demonstrate

accessing an element from a Dictionary

Creating a Dictionary

Dict = {1: 'Geeks', 'name': 'For', 3: 'Geeks'}

accessing a element using key

print(Dict['name'])

accessing a element using get()

print(Dict.get(3))

`

**Output:

For
Geeks

**Removing Elements from Dictionary: Using pop() and popitem()

Python `

Initial Dictionary

Dict = { 5 : 'Welcome', 6 : 'To', 7 : 'Geeks',
'A' : {1 : 'Geeks', 2 : 'For', 3 : 'Geeks'}, }

using pop()

Dict.pop(5) print(Dict)

using popitem()

Dict.popitem() print(Dict)

`

**Output:

{'A': {1: 'Geeks', 2: 'For', 3: 'Geeks'}, 6: 'To', 7: 'Geeks'}
{6: 'To', 7: 'Geeks'}

**Note: For more information, refer Python Dictionary.

**Refer to the below articles to know more about dictionary:

Decision Making

Decision Making in programming is similar to decision making in real life. A programming language uses control statements to control the flow of execution of the program based on certain conditions. These are used to cause the flow of execution to advance and branch based on changes to the state of a program.

**Decision-making statements in Python

**Example 1: To demonstrate if and if-else

Python `

Python program to demonstrate

decision making

a = 10 b = 15

if to check even number

if a % 2 == 0: print("Even Number")

if-else to check even or odd

if b % 2 == 0: print("Even Number") else: print("Odd Number")

`

**Output:

Even Number
Odd Number

**Example 2: To demonstrate nested-if and if-elif

Python `

Python program to demonstrate

decision making

a = 10

Nested if to check whether a

number is divisible by both 2 and 5

if a % 2 == 0: if a % 5 == 0: print("Number is divisible by both 2 and 5")

is-elif

if (a == 11): print ("a is 11") elif (a == 10): print ("a is 10") else: print ("a is not present")

`

**Output:

Number is divisible by both 2 and 5
a is 10

Control flow (Loops)

Loops in programming come into use when we need to repeatedly execute a block of statements. For example: Suppose we want to print “Hello World” 10 times. This can be done with the help of loops. The loops in Python are:

**While and while-else loopwhile-loop Python ``

</p><pre><code class="language-python3"></code></pre><p></p><pre></pre><p><br></p><p dir="ltr"><br></p><pre><code><span># Python program to illustrate  </span></code><br><code><span># while and while-else loop</span></code><br><code><span>i = 0</span></code><br><code><span>while (i < 3):      </span></code><br><code><span>    i = i + 1</span></code><br><code><span>    print("Hello Geek")  </span></code><br><code><span>   </span></code><br><code><span># checks if list still </span></code><br><code><span># contains any element  </span></code><br><code><span>a = [1, 2, 3, 4] </span></code><br><code><span>while a: </span></code><br><code><span>    print(a.pop()) </span></code><br><code><span>   </span></code><br><code><span>i = 10</span></code><br><code><span>while i < 12:  </span></code><br><code><span>    i += 1</span></code><br><code><span>    print(i)  </span></code><br><code><span>    break</span></code><br><code><span>else: # Not executed as there is a break  </span></code><br><code><span>    print("No Break")</span></code><br></pre><p dir="ltr"><b><strong>Output:</strong></b></p><pre><span>Hello Geek</span><br><span>Hello Geek</span><br><span>Hello Geek</span><br><span>4</span><br><span>3</span><br><span>2</span><br><span>1</span><br><span>11</span></pre><p dir="ltr"><a href="https://www.geeksforgeeks.org/python-for-loops/" target="_blank" rel="noopener"><b><strong>For and for-else loop</strong></b></a><img src="https://media.geeksforgeeks.org/wp-content/uploads/20191226130622/for-loop-python1.jpg" alt="for-loop-python" width="620" height="381" loading="lazy"></p><gfg-tabs data-run-ide="true" data-mode="light"><gfg-tab slot="tab">Python</gfg-tab><gfg-panel slot="panel" data-code-lang="python3"><pre><code class="language-python3"># Python program to illustrate  
# Iterating over a list  
print("List Iteration")  
l = ["geeks", "for", "geeks"]  
for i in l:  
    print(i) 
     
# Iterating over a String  
print("\nString Iteration")      
s = "Geeks"
for i in s :  
    print(i)  
     
print("\nFor-else loop")
for i in s:  
    print(i)  
else: # Executed because no break in for  
    print("No Break\n")  
   
for i in s:  
    print(i)  
    break
else: # Not executed as there is a break  
    print("No Break")

**Output:

List Iteration
geeks
for
geeks

String Iteration
G
e
e
k
s

For-else loop
G
e
e
k
s
No Break

G

**range() function: range() allows user to generate a series of numbers within a given range. Depending on how many arguments user is passing to the function. This function takes three arguments.**1) start: integer starting from which the sequence of integers is to be returned
**2) stop: integer before which the sequence of integers is to be returned.
**3) step: integer value which determines the increment between each integer in the sequence
filter_nonePythonRange

Python `

Python program to demonstrate

range() function

for i in range(5): print(i, end =" ") print()

for i in range(2, 9): print(i, end =" ") print()

incremented by 3

for i in range(15, 25, 3): print(i, end =" ")

`

**Output:

0 1 2 3 4
2 3 4 5 6 7 8
15 18 21 24

**Refer to the below articles to know more about Loops:

Loop control statements

Loop control statements change execution from its normal sequence. Following are the loop control statements provided by Python:

Python program to demonstrate

break, continue and pass

s = 'geeksforgeeks'

for letter in s: if letter == 'e' or letter == 's': break print(letter, end = " ") print()

for letter in s: if letter == 'e' or letter == 's': continue print(letter, end = " ") print()

for letter in s: if letter == 'e' or letter == 's': pass print(letter, end = " ")

`

**Output:

g
g k f o r g k
g e e k s f o r g e e k s

Functions

Functions are generally the block of codes or statements in a program that gives the user the ability to reuse the same code which ultimately saves the excessive use of memory, acts as a time saver and more importantly, provides better readability of the code. So basically, a function is a collection of statements that perform some specific task and return the result to the caller. A function can also perform some specific task without returning anything. In Python, def keyword is used to create functions.

Python `

Python program to demonstrate

functions

Defining functions

def ask_user(): print("Hello Geeks")

Function that returns sum

of first 10 numbers

def my_func(): a = 0 for i in range(1, 11): a = a + i return a

Calling functions

ask_user() res = my_func() print(res)

`

**Output:

Hello Geeks
55

Function with arguments

Python program to demonstrate

default arguments

def myFun(x, y = 50): print("x: ", x) print("y: ", y)

Driver code

myFun(10)

`

**Output:

('x: ', 10)
('y: ', 50)

Python program to demonstrate Keyword Arguments

def student(firstname, lastname):
print(firstname, lastname)

Keyword arguments

student(firstname ='Geeks', lastname ='Practice')
student(lastname ='Practice', firstname ='Geeks')

`

**Output:

('Geeks', 'Practice')
('Geeks', 'Practice')

Python program to demonstrate

variable length arguments

variable arguments

def myFun1(*argv):
for arg in argv:
print(arg, end =" ")

variable keyword arguments

def myFun2(**kwargs): for key, value in kwargs.items(): print ("% s == % s" %(key, value))

Driver code

myFun1('Hello', 'Welcome', 'to', 'GeeksforGeeks') print() myFun2(first ='Geeks', mid ='for', last ='Geeks')

`

**Output:

Hello Welcome to GeeksforGeeks
first == Geeks
last == Geeks
mid == for

**Note: For more information, refer Functions in Python.

**Refer to the below articles to know more about functions:

Lambda functions

In Python, the lambda/anonymous function means that a function is without a name. The lambda keyword is used to create anonymous functions. Lambda function can have any number of arguments but has only one expression.

Python `

Python code to demonstrate

labmda function

Cube using lambda

cube = lambda x: x * x*x
print(cube(7))

List comprehension using lambda

a = [(lambda x: x * 2)(x) for x in range(5)] print(a)

`

**Output:

343
[0, 2, 4, 6, 8]

**Note: For more information, refer Python lambda (Anonymous Functions).

Object Oriented Programming

Object-oriented programming aims to implement real-world entities like inheritance, hiding, polymorphism, etc in programming. The main aim of OOP is to bind together the data and the functions that operate on them so that no other part of the code can access this data except that function.

Python-OOPS-Concept

Classes and Objects

Class creates a user-defined data structure, which holds its own data members and member functions, which can be accessed and used by creating an instance of that class. A class is like a blueprint for an object.

An Object is an instance of a Class. A class is like a blueprint while an instance is a copy of the class with actual values.

Python `

Python code to demonstrate

labmda function

Cube using lambda

cube = lambda x: x * x*x
print(cube(7))

List comprehension using lambda

a = [(lambda x: x * 2)(x) for x in range(5)] print(a)

`

**Output:

mamal
I'm a mamal
I'm a dog

**The self

self represents the instance of the class. By using the “self” keyword we can access the attributes and methods of the class in python. It binds the attributes with the given arguments.

**Note: For more information, refer self in Python class.

Constructors and Destructors

**Constructors: Constructors are generally used for instantiating an object.The task of constructors is to initialize(assign values) to the data members of the class when an object of class is created. In Python the __init__() method is called the constructor and is always called when an object is created. There can be two types of constructors:

Python program to demonstrate

constructors

class Addition: # parameterized constructor def init(self, f, s): self.first = f self.second = s

def calculate(self):
    print(self.first + self.second)

Invoking parameterized constructor

obj = Addition(1000, 2000)

perform Addition

obj.calculate()

`

**Output:

3000

**Destructors: Destructors are called when an object gets destroyed. The __del__() method is a known as a destructor method in Python. It is called when all references to the object have been deleted i.e when an object is garbage collected.

Python `

class Employee: 

# Initializing 
def __init__(self): 
    print('Employee created.') 

# Deleting (Calling destructor) 
def __del__(self): 
    print('Destructor called, Employee deleted.')

obj = Employee() del obj

`

**Output:

Employee created.
Destructor called, Employee deleted.

Inheritance

Inheritance is the ability of any class to extract and use features of other classes. It is the process by which new classes called the derived classes are created from existing classes called Base classes.

Python `

A Python program to demonstrate inheritance

class Person(): 

# Constructor 
def __init__(self, name): 
    self.name = name 

# To get name 
def getName(self): 
    return self.name 

# To check if this person is employee 
def isEmployee(self): 
    return False

Inherited or Sub class (Note Person in bracket)

class Employee(Person): 

# Here we return true 
def isEmployee(self): 
    return True

Driver code

emp = Person("Geek1") # An Object of Person print(emp.getName(), emp.isEmployee())

emp = Employee("Geek2") # An Object of Employee print(emp.getName(), emp.isEmployee())

`

**Output:

Geek1 False
Geek2 True

**Note: For more information, refer Python inheritance.

Encapsulation

Encapsulation describes the idea of wrapping data and the methods that work on data within one unit. This puts restrictions on accessing variables and methods directly and can prevent the accidental modification of data.

Python `

Python program to demonstrate

encapsulation

Creating a Base class

class Base: def init(self): self.a = "GeeksforGeeks" self.__c = "GeeksforGeeks"

Creating a derived class

class Derived(Base): def init(self): 

    # Calling constructor of 
    # Base class
    Base.__init__(self)  
    print("Calling private member of base class: ") 
    print(self.__a)

Driver code

obj = Derived()

`

**Output:

Traceback (most recent call last):
File "/home/5a605c59b5b88751d2b93dd5f932dbd5.py", line 20, in
obj = Derived()
File "/home/5a605c59b5b88751d2b93dd5f932dbd5.py", line 18, in init
print(self.__a)
AttributeError: 'Derived' object has no attribute '_Derived__a'

Polymorphism

Polymorphism refers to the ability of OOPs programming languages to differentiate between entities with the same name efficiently. This is done by Python with the help of the signature of these entities.

Python `

Python program to demonstrate

Polymorphism

class A(): def show(self): print("Inside A")

class B(): def show(self): print("Inside B")

Driver's code

a = A() a.show() b = B() b.show()

`

**Output:

Inside A
Inside B

**Refer to the articles to know more about OOPS:

File Handling

File handling is the ability of Python to handle files i.e. to read and write files along with many other file handling options. Python treats files differently as text or binary and this is important. Each line of code includes a sequence of characters and they form a text file. Each line of a file is terminated with a special character, called the **EOL or End of Line characters like comma {, } or newline character.

Basic File Handling operations in Python are:

**1) Open a file: Opening a file refers to getting the file ready either for reading or for writing. This can be done using the open() function. This function returns a file object and takes two arguments, one that accepts the file name and another that accepts the mode(Access Mode). Python provides six Access Modes:

ACCESS MODE DESCRIPTION
Read Only (‘r’) Open text file for reading. The handle is positioned at the beginning of the file.
Read and Write (‘r+’) Open the file for reading and writing. The handle is positioned at the beginning of the file.
Write Only (‘w’) Open the file for writing. For existing file, the data is truncated and over-written. The handle is positioned at the beginning of the file.
Write and Read (‘w+’) Open the file for reading and writing. For existing file, data is truncated and over-written. The handle is positioned at the beginning of the file.
Append Only (‘a’) Open the file for writing. The handle is positioned at the end of the file.
Append and Read (‘a+’) Open the file for reading and writing. The handle is positioned at the end of the file.

Python `

Python program to demonstrate

Polymorphism

class A(): def show(self): print("Inside A")

class B(): def show(self): print("Inside B")

Driver's code

a = A() a.show() b = B() b.show()

`

**Note: For more information, refer Open a File in Python.

**2) Close the file: close() function closes the file and frees the memory space acquired by that file.

Python `

Opening and Closing a file "MyFile.txt"

for object name file1.

file1 = open("MyFile.txt", "a") file1.close()

`

**3) Reading from a File: There are three ways to read data from a text file.

Let’s suppose the file looks like this:

python-file-handling

Python `

Program to show various ways to

read data from a file.

file1 = open("data.txt", "r+")

print("Output of Read function is ") print(file1.read()) print()

seek(n) takes the file handle to the nth

bite from the beginning.

file1.seek(0)

print("Output of Readline function is ") print(file1.readline()) print()

file1.seek(0)

readlines function

print("Output of Readlines function is ") print(file1.readlines()) print() file1.close()

`

**Output:

Output of Read function is
Code is like humor. When you have to explain it, its bad.

Output of Readline function is
Code is like humor. When you have to explain it, its bad.

Output of Readlines function is
['Code is like humor. When you have to explain it, its bad.']

**Note: For more information, refer How to read from a file in Python.

**4) Writing to a file: There are two ways to write in a file.

Python program to demonstrate

writing to file

Opening a file

file1 = open('myfile.txt', 'w') L = ["This is Delhi \n", "This is Paris \n", "This is London \n"] s = "Hello\n"

Writing a string to file

file1.write(s)

Writing multiple strings

at a time

file1.writelines(L)

Closing file

file1.close()

`

**Output:

python-writing-to-file

**Note: For more information, refer Writing to file in Python.

**Refer to the below articles to know more about File-Handling:

Modules and Packages

Modules

A module is a self-contained Python file that contains Python statements and definitions, like a file named GFG.py, which can be considered as a module named GFG which can be imported with the help of import statement.

Let’s create a simple module named GFG.

Python `

Python program to demonstrate

modules

Defining a function

def Geeks(): print("GeeksforGeeks")

Defining a variable

location = "Noida"

Defining a class

class Employee():

def __init__(self, name, position):
    self. name = name
    self.position = position
      
def show(self):
    print("Employee name:", self.name)
    print("Employee position:", self.position)

`

To use the above created module, create a new Python file in the same directory and import GFG module using the import statement.

Python `

Python program to demonstrate

modules

Defining a function

def Geeks(): print("GeeksforGeeks")

Defining a variable

location = "Noida"

Defining a class

class Employee():

def __init__(self, name, position):
    self. name = name
    self.position = position
      
def show(self):
    print("Employee name:", self.name)
    print("Employee position:", self.position)

`

**Output:

GeeksforGeeks
Noida
Employee name: Nikhil
Employee position: Developer

**Note: For more information, refer Python Modules.

Packages

Packages are a way of structuring many packages and modules which helps in a well-organized hierarchy of data set, making the directories and modules easy to access.

To create a package in Python, we need to follow these three simple steps:

**Example: Let’s create a package for cars.

Now, let’s use the package that we created. To do this make a sample.py file in the same directory where Cars package is located and add the following code to it:

Python `

Import classes from your brand new package

from Cars import Bmw from Cars import Audi

Create an object of Bmw class & call its method

ModBMW = Bmw() ModBMW.outModels()

Create an object of Audi class & call its method

ModAudi = Audi() ModAudi.outModels()

`

**Output:

python-packages1

**Note: For more information, refer Create and Access a Python Package.

Regular expressions(RegEx)

Python RegEx is a powerful text matching tool that uses a pre-defined pattern to match the text. It can identify the presence or absence of text by comparing it to a specific pattern, and it can also divide a pattern into one or more sub-patterns. Below is the list of metacharacters:

\ Used to drop the special meaning of character
following it (discussed below)
[] Represent a character class
^ Matches the beginning
$ Matches the end
. Matches any character except newline
? Matches zero or one occurrence.
| Means OR (Matches with any of the characters
separated by it.

The most frequently used methods are:

**re.findall(): Return all non-overlapping matches of pattern in string, as a list of strings. The string is scanned left-to-right, and matches are returned in the order found.

Python `

A Python program to demonstrate working of

findall()

import re

string = """Hello my Number is 123456789 and my friend's number is 987654321"""

A sample regular expression to find digits.

regex = '\d+'

match = re.findall(regex, string) print(match)

`

**Output:

['123456789', '987654321']

In the above example, metacharacter blackslash

‘\’

has a very important role as it signals various sequences. If the blackslash is to be used without its special meaning as metacharacter, use

’\\’

.<>

\d Matches any decimal digit, this is equivalent
to the set class [0-9].
\D Matches any non-digit character.
\s Matches any whitespace character.
\S Matches any non-whitespace character
\w Matches any alphanumeric character, this is
equivalent to the class [a-zA-Z0-9_].
\W Matches any non-alphanumeric character.

**re.compile(): Regular expressions are compiled into pattern objects, which have methods for various operations such as searching for pattern matches or performing string substitutions.

Python `

A Python program to demonstrate working of

compile()

import re

it is equivalent to [abcde].

p = re.compile('[a-e]')

print(p.findall("Aye, said Mr. Gibenson Stark"))

`

**Output:

['e', 'a', 'd', 'b', 'e', 'a']

**re.match(): This function attempts to match pattern to whole string. The re.match function returns a match object on success, None on failure.

Python `

A Python program to demonstrate working

of re.match().

import re

def findMonthAndDate(string): 

regex = r"([a-zA-Z]+) (\d+)"
match = re.match(regex, string) 
   
if match == None:  
    print("Not a valid date")
    return

print("Given Data: % s" % (match.group()))
print("Month: % s" % (match.group(1)))
print("Day: % s" % (match.group(2)))

Driver Code

findMonthAndDate("Jun 24") print("") findMonthAndDate("I was born on June 24")

`

**Output:

Given Data: Jun 24
Month: Jun
Day: 24

Not a valid date

**re.search(): This method either returns None (if the pattern doesn’t match), or a re.MatchObject that contains information about the matching part of the string.

Python `

A Python program to demonstrate working of re.match().

import re

regex = r"([a-zA-Z]+) (\d+)"

match = re.search(regex, "I was born on June 24")

if match != None: 

print("Match at index % s, % s" % (match.start(), match.end()))

# this will print "June 24" 
print("Full match: % s" % (match.group(0)))

# this will print "June" 
print("Month: % s" % (match.group(1)))

# this will print "24" 
print("Day: % s" % (match.group(2)))

else: print("The regex pattern does not match.")

`

**Output:

Match at index 14, 21
Full match: June 24
Month: June
Day: 24

**Note: For more information, refer Regular Expression in Python.

Exception handling

Like other languages, Python also provides the runtime errors via exception handling method with the help of try-except.

**How try-except works?

**Code 1: No exception, so try clause will run.

Python `

Python code to illustrate

working of try()

def divide(x, y): try: result = x // y print("Yeah ! Your answer is :", result) except ZeroDivisionError: print("Sorry ! You are dividing by zero ")

Look at parameters and note the working of Program

divide(3, 2)

`

**Output:

Yeah ! Your answer is : 1

**Code 2: There is an exception so only except clause will run.

Python `

Python code to illustrate

working of try()

def divide(x, y): try: result = x // y print("Yeah ! Your answer is :", result) except: print("Sorry ! You are dividing by zero ")

Look at parameters and note the working of Program

divide(3, 0)

`

**Output:

Sorry ! You are dividing by zero

**Else Clause: In python, you can also use else clause on try-except block which must be present after all the except clauses. The code enters the else block only if the try clause does not raise an exception.

Python `

Python code to illustrate

working of try()

def divide(x, y): try: result = x // y print("Yeah ! Your answer is :", result) except: print("Sorry ! You are dividing by zero ") else: print("No exception raised")

Look at parameters and note the working of Program

divide(3, 2)

`

**Output:

Yeah ! Your answer is : 1
No exception raised

**Raising Exception: The raise statement allows the programmer to force a specific exception to occur. This must be either an exception instance or an exception class. To know more about the list of exception class click here.

Python `

Program to depict Raising Exception

try:
raise NameError("Hi there") # Raise Error except NameError: print("An exception") raise # To determine whether the exception was raised or not

`

**Output:

Traceback (most recent call last):
File "/home/4678cd3d633b2ddf9d19fde6283f987b.py", line 4, in
raise NameError("Hi there") # Raise Error
NameError: Hi there

**Note: For more information, refer Python exception handling.