Standard Library

Number Parsing

int() and float() parse text into numbers and raise ValueError on bad input.

Use int() for whole numbers and float() for decimal text. Parsed values are real numbers, not strings.

Source

print(int("42"))
print(float("3.5"))

Output

42
3.5

Pass a base when the text format says the number is not decimal.

Source

print(int("ff", 16))

Output

Catch ValueError at the input boundary when invalid text is normal and recoverable.

Source

texts = ["10", "python", "20"]
for text in texts:
    try:
        print(int(text) * 2)
    except ValueError:
        print(f"skip {text!r}")

Output

20
skip 'python'
40

Notes

int() and float() are constructors that also parse strings.
int(text, base) makes non-decimal input explicit.
Catch ValueError for recoverable user input; do not hide unexpected data corruption.

Run the complete example

42
3.5
255
20
skip 'python'
40

Execution time appears here after you run the example.