How do I parse a string to a float or int?

Question

In Python, how can I parse a numeric string like \"545.2222\" to its corresponding float value, 545.2222? Or parse the string \"31\" t

Answer 1

I am surprised nobody mentioned regex because sometimes string must be prepared and normalized before casting to number

import re
def parseNumber(value, as_int=False):
    try:
        number = float(re.sub('[^.\-\d]', '', value))
        if as_int:
            return int(number + 0.5)
        else:
            return number
    except ValueError:
        return float('nan')  # or None if you wish

usage:

parseNumber('13,345')
> 13345.0

parseNumber('- 123 000')
> -123000.0

parseNumber('99999\n')
> 99999.0

and by the way, something to verify you have a number:

import numbers
def is_number(value):
    return isinstance(value, numbers.Number)
    # will work with int, float, long, Decimal