replacement for fpformat.extract

[Gribouillis]

Here is the Python 2 code of fpformat.extract(), you could perhaps convert this function directly, or it may run out of the box in Python 3.

# Compiled regular expression to "decode" a number
decoder = re.compile(r'^([-+]?)(\d*)((?:\.\d*)?)(([eE][-+]?\d+)?)$')
# \0 the whole thing
# \1 leading sign or empty
# \2 digits left of decimal point
# \3 fraction (empty or begins with point)
# \4 exponent part (empty or begins with 'e' or 'E')

try:
    class NotANumber(ValueError):
        pass
except TypeError:
    NotANumber = 'fpformat.NotANumber'

def extract(s):
    """Return (sign, intpart, fraction, expo) or raise an exception:
    sign is '+' or '-'
    intpart is 0 or more digits beginning with a nonzero
    fraction is 0 or more digits
    expo is an integer"""
    res = decoder.match(s)
    if res is None: raise NotANumber, s
    sign, intpart, fraction, exppart = res.group(1,2,3,4)
    intpart = intpart.lstrip('0');
    if sign == '+': sign = ''
    if fraction: fraction = fraction[1:]
    if exppart: expo = int(exppart[1:])
    else: expo = 0
    return sign, intpart, fraction, expo