Python implementation of parseInt, which converts a value to a string, then reads until the first non-number.

js-parseint.py

ZERO = ord("0")
NINE = ord("9")


def parseInt(s):
    result = None
    for i in str(s):
        ascii_value = ord(i)
        if ZERO <= ascii_value <= NINE:
            result = result or 0
            result *= 10
            result += ascii_value - ZERO
        else:
            break
    return result


print(parseInt(0.5))  # 0
print(parseInt(0.05))  # 0
print(parseInt(0.005))  # 0
print(parseInt(0.0005))  # 0
print(parseInt(0.00005))  # 5, note: python starts using scientific notation here
print(parseInt(0.000005))  # 5
print(parseInt(0.0000005))  # 5