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18. Basic Data Types

1. Introduction​

Python has several built-in data types that form the foundation of the language.
Understanding these is essential because you will use them in almost every program.

2. Numbers​

Python has different types of numbers:

  • Integers (int) → whole numbers
  • Floating-point numbers (float) → decimal numbers
  • Complex numbers (complex) → numbers with real and imaginary parts

Examples:

a = 10        # int
b = 3.14      # float
c = 2 + 3j    # complex

Check their types:

print(type(a))  # <class 'int'>
print(type(b))  # <class 'float'>
print(type(c))  # <class 'complex'>

3. Strings​

A string is text enclosed in quotes.

name = "Alice"
greeting = 'Hello, world!'

Strings can be joined:

first = "Py"
second = "thon"
print(first + second)  # Python

4. Booleans​

A boolean is either True or False.

is_active = True
is_logged_in = False

Booleans often come from comparisons:

print(5 > 3)   # True
print(2 == 4)  # False

5. None​

None is a special type representing the absence of a value.

result = None
print(result)  # None

6. Lists​

A list is an ordered, changeable collection.

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

Lists can be modified:

fruits.append("orange")
print(fruits)  # ['apple', 'banana', 'cherry', 'orange']

7. Tuples​

A tuple is an ordered, unchangeable collection.

point = (3, 4)
print(point[0])  # 3

8. Sets​

A set is an unordered collection of unique items.

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

9. Dictionaries​

A dictionary stores data as key-value pairs.

person = {"name": "Alice", "age": 25}
print(person["name"])  # Alice

10. Dynamic Typing in Python​

You can reassign a variable to a different type:

x = 10
print(type(x))  # int
x = "hello"
print(type(x))  # str

11. Checking Data Types​

Use type() and isinstance():

x = 3.14
print(type(x))               # <class 'float'>
print(isinstance(x, float))  # True

12. Next Steps​

✅ You now know Python’s basic data types: numbers, strings, booleans, None, lists, tuples, sets, and dictionaries.
In the next chapter, we’ll learn about type conversion and casting.