Good handling of input data (was Re: Newbie question)

[Steven D'Aprano]

On Tue, 06 Mar 2007 05:57:43 -0500, Tommy Grav wrote:

> So how would you handle this type of error handling?
> My main problem is that occasionally there is an entry
> in the list that is a string:
> 
> 0.9834 134.4933 78.009 run11 27

How do you want to deal with such an occasional string? What do you expect
the code to do?

The way I see it, if you're expecting five floats, and you get four floats
and a string, that's an error. Do you ignore the entire line, or replace
the string with zero, or what?


> Again I would like to avoid having to individually parse the 3 floats,
> while still easily handling the string, but a list comprehension will
> not work as far as I can tell. Is there a module that handles this
> type of flat ascii tables? Something like:
> 
> (x,y,z,id,n) = ParseFile("float","float","float","string","int")
> 
> would be great, and I guess
> 
> (x,y,z,id,n) = PaseFile2("%f %f %f %s %d")
> 
> would be even better.

How about this?

def parse_line(line, types):
    items = line.split()
    return [t(s) for (t, s) in zip(types, items)]


>>> line = "  4.5  6.7    23    -1 fred   7.9  "
>>> parse_line(line, (float, float, int, int, str, float))
[4.5, 6.7000000000000002, 23, -1, 'fred', 7.9000000000000004]



-- 
Steven.