Convert Python strings into floats explicitly using the comma or the point as separators

Question

How can I explicitly tell python to read a decimal number using the point or the comma as a decimal separator? I don't know the localization settings of the PC that will run my script, and this should not influence my application, I only want to say:

f = read_float_with_point("3.14")

or

f = read_float_with_comma("3,14")

I think that writing

def read_float_with_comma(num):
    return float(num.replace(",", ".")

is not secure, because I don't know the locale settings!

Answer 1

You can use babel to parse decimals in local formats:

>>> parse_decimal('1,099.98', locale='en_US')
Decimal('1099.98')
>>> parse_decimal('1.099,98', locale='de')
Decimal('1099.98')

Answer 2

because I don't know the locale settings

You could look that up using the locale module:

>>> locale.nl_langinfo(locale.RADIXCHAR)
'.'

or

>>> locale.localeconv()['decimal_point']
'.'

Using that, your code could become:

import locale
_locale_radix = locale.localeconv()['decimal_point']

def read_float_with_comma(num):
    if _locale_radix != '.':
        num = num.replace(_locale_radix, ".")
    return float(num)

Better still, the same module has a conversion function for you, called atof():

import locale

def read_float_with_comma(num):
    return locale.atof(num)

Answer 3

You can use locale.atof

import locale
locale.atof('12.3')

http://docs.python.org/2/library/locale.html