Why does input() return a string in Python?

Short answer

input() always returns a str, even when the user types digits. Wrap it in int() or float() immediately, or arithmetic will fail with a TypeError.

Python has no way to know whether 42 should be a number, a house number, or a product code. Rather than guess, it hands you exactly what was typed.

python

age = input("How old are you? ")   # user types 30
print(age + 10)                    # TypeError: can only concatenate str

Convert at the boundary — the same line the value arrives on:

python

age = int(input("How old are you? "))
print(f"In ten years you will be {age + 10}.")

#Handle input that is not a number

int() raises ValueError on anything it cannot parse. Wrap it:

python

while True:
    try:
        age = int(input("How old are you? "))
        break
    except ValueError:
        print("Please enter a whole number.")

That loop is the standard shape for any prompt that must produce a number.

#The subtle one

int("3.7") also fails. int parses integers, not decimals. If you might get either, use float() first and round or truncate afterwards.

#Handle input that is not a number

#The subtle one

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