Python Variables

A variable is the name given to a memory location. A value-holding Python variable is also known as an identifier.

Since Python is an infer language that is smart enough to determine the type of a variable, we do not need to specify its type in Python.

Variable names must begin with a letter or an underscore, but they can be a group of both letters and digits.

How to Create a Variable

To begin with, let’s state that the assignment of a variable with an equal sign(=) is carried out within the set of constructs in Python.

x = 10   #  Here we are declaring variable x and assigning it the value 10.

name = "Alice"   # Here we are declaring a variable called name and assigning it the value Alice.

Rules for Naming Variables

1. Start with a letter or an underscore:

Allowed: name, _name
Not allowed: 1name, @name

2. It can contain letters, numbers and underscores:

Examples: user_name, age1

3. No spaces or special characters:

Use underscores _ in place of spaces.

4. Case-sensitive:

Name and name are different variables

5. Don’t use Python reserved keywords:

Keywords like if, else, while, etc, cannot be used as variable names.

Assigning Values to Variables

You can give any type of value to a variable:

Numbers



age = 25   # Integer
height = 5.9   # Float

Strings (Text)



greeting = "Hello, world!"

Boolean (True or False)



is_active = True

Lists (Collection of items)



colors = ["red", "green", "blue"]

Other Data Types
Python also supports more complex data types like dictionaries, tuples, etc.

Changing Variable Values

One can change a variable’s value in the script by simply reassigning it:


x=10   # x is initially 10
x=20   # x is now 20

Dynamic Typing

Python is dynamically typed, which means you don’t need to declare the type of a variable. It can change its type during the program’s execution.

code x = 10    # x is an integer

x = "Python"   # Now x is a string

Multiple Variable Assignments

Assigning the same value to multiple variables:


      a = b = c = 5

Assigning different values to multiple variables in one line:


      x, y, z = 1, 2, 3

Printing Variable Values

Use the print() to display the value of a variable:

name = "Alice"

print(name)   #  Output:  Alice

Why Variables Are Useful

Reusability: Use the same variable throughout the program.
Readability: Makes your code more understandable.
Flexibility: Change the value without altering the rest of the code.

Best Practices for Variables

1. Use meaningful names:

Bad: x = 25
Good: age = 25

2. Stick to lowercase for simple variable names (snake_case is common in Python):

Example: user_name, total_score

3. Avoid overly long names but make them descriptive:

Good: average_temperature
Too long: the_average_temperature_of_today_in_city

Example: Variables in Action

#  Storing a person's details
name = "Alice"
age = 30
is_member = True

#  Displaying details
print("Name:", name)
print("Age:", age)
print("Membership Status:", is_member)

#  Updating age
age = 31
print("Updated Age:", age)