pyt...@bdurham.com <pyt...@bdurham.com> wrote:
> Thanks for everyone's feedback. I believe my original post's code
> (updated following my signature) was in line with this list's feedback.
>
> Christian: Thanks for reminding me about exponential formats. My updated
> code accounts for these type of numbers. I don't need to handle inf or
> nan values. My original code's except catches an explicit ValueError
> exception per your concern about bare excepts.
>
> Malcolm
>
> <code>
> # str_to_num.py
>
> def isnumber( input ):
> try:
> num = float( input )
> return True
>
> except ValueError:
> return False
That is a fine solution.
Last time I had to solve this I had a specific format of number to
parse - I didn't want to include all the python formats. This is what
I came up with... This particular code returns the converted number
or 0.0 - adjust as you see fit!
import re
_float_pattern = re.compile(r"^\s*([-+]?(\d*\.)?\d+([eE][-+]?\d+)?)")
def atof(value):
"""
Convert a string to an float in the same way the c-library atof()
does. Ie only converting as much as it can and returning 0.0 for
an error.
"""
match = _float_pattern.search(value)
if match:
return float(match.group(1))
return 0.0
>>> atof("15.5 Sausages")
15.5
>>> atof(" 17.2")
17.199999999999999
>>> atof("0x12")
0.0
>>> atof("8.3.2")
8.3000000000000007
>>> atof("potato")
0.0
>>>
--
Nick Craig-Wood <n...@craig-wood.com> -- http://www.craig-wood.com/nick
--
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