Numeric Conversion

[Justin Sheehy]

Iddo Friedberg <idoerg at cc.huji.ac.il> writes:

> My problem: I have text files with fields which are either numeric, or
> not. I'd like to convert the numeric ones into numerical values, while
> keeping the rest as strings. I initially did that by trapping the
> exceptions that atoi() & atol() generate upon hitting a non-numeric
> string, but atoi('+') does not generate an exception.
> 
> Anything I can do about it? I managed to solve the problem with regexp
> matching:
> 
> >>>
> myfloat=re.compile('^[+-]{0,1}\d+\.\d*$|^[+-]{0,1}\d*\.\d*[Ee][+-]*\d+$|^[+-]{0,1}\.\d+$')
> 
> Is there a more elegant solution? (regexpwise or otherwise, I admit I'm
> not a very sophisticated user of regexps, AAMOF, I'm PERL illiterate).

Pretty much anything other than regexps would be more elegant.  ;-)

I would use int() (and/or float(), if appropriate) and trap the
exceptions, much as you were using string.atoi().

Hm.  Actually, now that I test it, string.atoi() does seem to
correctly throw exceptions on '+' and '-' in my setup.  (1.5.2)

This appears to have changed sometime between 1.4 and 1.5.2.

-Justin