int/float conversion

Learn safe conversion with int(input()) and float(input()).

int() and float() conversion

Because input() returns a string, you must convert it to a number for arithmetic. int() converts to an integer, float() to a decimal:

age = int(input("Yaş: "))
price = float(input("Fiyat: "))
print(age * 2)      # 36
print(price + 1)    # 11.5

The content must be a valid numeric string. If it contains non-numeric characters, it raises ValueError.

This pattern — input followed by conversion — is standard for numeric input.

Conversion errors

If a string cannot be parsed as a number, a ValueError is raised. For example int("abc") or int("3.14") fail — int("3.14") does not work because the dot is not part of integer syntax:

int("abc")    # ValueError
int("3.14")   # ValueError
float("3.14") # 3.14 — OK
int("42")     # 42 — OK

To convert a decimal string safely, first use float(), then int(). To catch bad input, the conversion must be wrapped in a guard block; this is covered later.

Exercise Read price and double it

Assign float(input("Fiyat: ")) to price. The user types 10. Then print the doubled price with print(price * 2).

Show example solution

price = float(input("Fiyat: "))
print(price * 2)

Test yourself

Complete the int conversion

age = ____(input("Yaş: "))

Show answer

age = int(input("Yaş: "))

Match conversions

int("42")

42
float("3.14")

3.14
int("abc")

ValueError
float("42")

42.0
What does float('42') return?
- 42.0 (float)
- 42 (int)
- '42' (string)
- ValueError
Show answer

42.0 (float) — float() converts a valid numeric string to a decimal.

Next lesson: print parameters

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