Basic Data Types in Python

Look at these two lines. The operator is the same, but the result is different:

Python 3.13
1
print(10 + 5)
15
2
print("10" + "5")
105

In the first case + added the numbers; in the second it glued two strings together. Python behaves differently because 10 and "10" are not the same thing to it: the first is a number, the second is text. Python attaches a type to every value, and it's the type that decides what an operation on that value means.

That's why mixing up types is a common source of beginner bugs: you add two values expecting 15 and get "105" instead, because the values were actually strings.

How to find out a value's type

If you're not sure what you're dealing with, you can ask for the type directly with the type() function.

Python 3.13
1
print(type(42))
<class 'int'>
2
print(type(3.14))
<class 'float'>
3
print(type("Python"))
<class 'str'>
4
print(type(True))
<class 'bool'>

In the output int is a whole number, float is a number with a fractional part, str is a string, bool is a boolean value (true or false). You don't declare the type up front: Python figures it out from what you wrote.

Python 3.13
1234
number = 42        # int  — a whole number
pi = 3.14          # float — a number with a fractional part
name = "Python"    # str  — a string
is_active = True   # bool — a boolean value

What types exist in Python

Besides the four basic ones, Python has built-in types for collections and more specialized tasks. Here are the main categories:

In the next few chapters we'll cover numbers, strings, and booleans in detail, then move on to collections — lists, tuples, sets, and dictionaries. For now one idea is enough: every value has a type, and that type decides what you can do with the value.

Check your understanding

What does print("3" + "4") output?