Getting Started

Python - IntroductionPython - Hello World ProgramPython - SyntaxPython - Data TypesPython - Variables

Operators

Python - Arithmetic OperatorsPython - Relational OperatorsPython - Logical OperatorsPython - Assignment OperatorsPython - Bitwise OperatorsPython - Membership OperatorsPython - Identity OperatorsPython - Increment and Decrement Operators

Conditions

Python - If Else statement

Loop

Python - While LoopPython - For Loop

Numbers

Python - NumbersPython - Number Conversion

Strings

Python - StringsPython - String OperatorsPython - String FormattingPython - String MethodsPython - String Format Method

List

Python - ListPython - List Methods

Tuple

Python - Tuple

Set

Python - SetPython - Set Methods

Dictionary

Python - DictionaryPython - Dictionary Methods

Functions

Python - FunctionsPython - Functions - Variable length argumentsPython - Lambda Function

Scope of Variables

Python - Scope of Variables

Modules

Python - ModulesPython - Math ModulePython - JSON ModulePython - datetime ModulePython - time Module

I/O

Python - Read input from keyboard

File

Python - File Handling

Exception Handling

Python - Exception Handling

OOP

Python - Classes and ObjectsPython - Class Constructor __init__ methodPython - Class Destructor __del__ methodPython - Built-in Class AttributesPython - InheritancePython - Method OverridingPython - Method Overloading

Package Management

Python - PIP

Python - MySQL

Python - MySQL - Getting StartedPython - MySQL - Insert dataPython - MySQL - Select dataPython - MySQL - Update dataPython - MySQL - Delete data

Python - CSV

Python - Read data from CSV filePython - Write data in CSV file

Python - Variables

Python

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In this tutorial we will learn to work with variables in Python.

Variables are named memory locations which holds some value. And these values can be changed later.

We don't have to explicitly declare variables in Python to reserve memory space. They are automatically declared and memory is allocated when a variable is assigned a value.

Creating Variables

Following are the rules that we must remember while naming a variable in Python.

  • We can only use letters (uppercase A-Z and lowercase a-z), digits (0-9) and underscore (_) to name a variable.
  • Variable name must start with a letter or underscore.
  • We can't start a variable name with digit.
  • Variable name is case-sensitive.

Following are some of the valid variable names.

isGameOver
x
y
sum
_avg
score1
score2

Following are invalid variable names.

1account      # can't start with digit
user-name     # con't use -

Case sensitive

Variables are case-sensitive in Python which means lowercase variable name and uppercase variable name are treated differently.

Following variables are treated differently even though they are the same word.

score = 10
SCORE = 10

Assign value to a variable

We use the = sign to assign value to a variable.

In the following example we are assigning integer value to a variable x.

x = 10

Same value assignment

We can assign same value in one go to multiple variables in Python.

In the following example we are assigning value 10 to the three variables.

x = y = z = 10

Different value assignment

We can assign different values in one go to different variables in Python.

In the following example we are assigning 1 to a, 3.14 to b, 'Hello World' to msg and 1+2j to c.

a, b, msg, c = 1, 3.14, 'Hello World', 1 + 2j

Swap value of variables

If there are two variables and we want to swap their values without using any third variable then we can write the following code in Python.

var1, var2 = var2, var1

In the following example we have two variables a and b and they hold values 10 and "Happy" respectively and we are swapping their values.

# before
a = 10
b = "Happy"
print("before:", a, b)

# swap
a, b = b, a

# after
print("after:", a, b)

We will get the following output.

before: 10 Happy
after: Happy 10