Python Variables

Understanding Variables and Literals in Python

Variables and literals are the foundation of any Python program. Whether you're storing user input, configuring logic, or displaying output, you'll be using these concepts constantly. This article explains what they are, how they work, and how to use them effectively.

What is a Variable?

A variable is a named container used to store data in memory. Think of it like a label on a box: the label (variable name) tells you what's inside the box (value). You can later change the content or use it in operations.

Creating and Using Variables

To create a variable, you simply assign it a value using the = operator.

username = "Alice"
age = 30
height = 1.75

• username stores a string ("Alice")
• age stores an integer (30)
• height stores a float (1.75)

Python automatically detects the type of data based on the value you assign. This is called dynamic typing.

Displaying Variable Values

print(username)
print(age)
print(height)

Output:

Alice
30
1.75

Reassigning Variables

Variables can be reassigned to new values at any time.

username = "Alice"
print(username)

username = "Bob"
print(username)

Output:

Alice
Bob

The variable username was updated from "Alice" to "Bob".

Multiple Assignment

You can assign multiple variables in a single line:

x, y, z = 1, 2.5, "Hello"
print(x)
print(y)
print(z)

Output:

1
2.5
Hello

You can also assign the same value to multiple variables:

a = b = c = "Python"
print(a)
print(b)
print(c)

Output:

Python
Python
Python

Rules for Naming Variables

When naming variables in Python:

• Names must begin with a letter or an underscore (_)
• Names can contain letters, digits, and underscores
• They cannot start with a digit
• They are case-sensitive (myVar is different from myvar)
• Avoid using Python keywords (like if, for, class)

Valid names: user_name, _temp, age2
Invalid names: 2name, user-name, class

What is a Literal?

A literal is a fixed value that appears directly in your code. It's the actual data you're assigning to a variable.

name = "David"   # "David" is a string literal
price = 9.99     # 9.99 is a float literal
is_active = True # True is a boolean literal

Types of Literals in Python

Numeric Literals

These represent numbers and come in three forms:

• Integers – Whole numbers, with or without a minus sign.

a = 42
b = -7

• Floating-point numbers – Numbers with a decimal point.

pi = 3.1415
temp = -2.0

• Complex numbers – Numbers with a real and imaginary part (j represents the imaginary unit).

c = 2 + 3j
print(c.real)   # 2.0
print(c.imag)   # 3.0

String Literals

Text surrounded by quotes is a string literal. You can use either single or double quotes.

message1 = "Hello, world!"
message2 = 'Python is fun.'

Multiline strings can be created using triple quotes:

note = """This is
a multiline
string."""
print(note)

Output:

This is
a multiline
string.

Boolean Literals

Python has two boolean literals: True and False.

is_valid = True
is_expired = False

These are often used in conditions and control flow.

Special Literal: None

None represents the absence of a value.

result = None
print(result)

Output:

None