Partie 6 — Variables and Data Types in Python (Complete Beginner Guide 2026)

Learn Python variables and data types step by step. Understand strings, integers, floats, booleans, lists, dictionaries, sets, type conversion, and best practices for beginners.

6. Variables and Data Types in Python

Variables and data types are the foundation of programming in Python. Every program you write will store, modify, and process data. Understanding how Python handles variables and different types of data is essential before moving to advanced topics.

Core Idea: A variable stores data, and a data type defines what kind of data it is.

1) What Is a Variable?

A variable is a name that refers to a value. In Python, you create a variable using the assignment operator =.

name = "Ali"
age = 25
price = 19.99

Python automatically detects the data type based on the assigned value.

Python is dynamically typed — you don’t need to declare the type explicitly.

2) Variable Naming Rules

Must start with a letter or underscore
Cannot start with a number
Cannot use reserved keywords (like if, for, class)
Use snake_case for readability

user_name = "Sara"
total_amount = 100
is_active = True

3) Basic Data Types in Python

A) String (str)

Strings represent text and are enclosed in quotes.

message = "Hello Python"
print(type(message))

B) Integer (int)

Integers are whole numbers.

age = 30
print(type(age))

C) Float (float)

Floats are numbers with decimal points.

price = 49.99
print(type(price))

D) Boolean (bool)

Boolean values represent True or False.

is_logged_in = True
print(type(is_logged_in))

4) Complex Data Types

A) List

Lists store multiple values in order.

fruits = ["apple", "banana", "orange"]
print(fruits[0])

B) Tuple

Tuples are similar to lists but cannot be modified.

coordinates = (10, 20)
print(coordinates)

C) Dictionary

Dictionaries store key-value pairs.

user = {"name": "Omar", "age": 22}
print(user["name"])

D) Set

Sets store unique values.

numbers = {1, 2, 3, 3}
print(numbers)

5) Type Conversion (Casting)

Sometimes you need to convert between types.

age = "25"
age_number = int(age)

price = 10
price_text = str(price)

Remember: input() always returns a string. Use int() or float() when needed.

6) Checking Data Types

value = 100
print(type(value))

The type() function helps you debug and understand what kind of data you are working with.

7) Best Practices

Use meaningful variable names
Avoid overwriting built-in names (like list, str, int)
Keep consistent naming style
Understand the type before performing operations

Strong understanding of variables and data types makes learning loops, functions, and advanced topics much easier.

Conclusion

Variables allow you to store data, and data types define how that data behaves. By mastering strings, numbers, booleans, lists, dictionaries, and type conversion, you build the core foundation of Python programming.

Practice by creating small examples and experimenting with different data types. The more you manipulate data, the more comfortable you become.