[Python-ideas] min_fields argument to str.split()

Tal Einat taleinat at gmail.com
Wed Jan 21 11:29:17 CET 2009


Calvin Spealman wrote:
> This might be a silly idea, but I was wondering about forcing split()
> to return at least X number of items. For example, I might be getting
> a comma separated string and i want to split it up into names, but I
> might have less than all of them. If it is just 0, 1, or 2, I can use
> partition(), but any more and that doesn't work. Besides, I don't care
> if the separator is there, just to get the values. Might also make
> sense to give the values to give by default.
>
> Example of implementing this:
>
> def split(self, sep=None, max_splits=None, min_items=None):
>    parts = self.split(sep, max_splits)
>    if len(parts) < min_items:
>        parts.extend([None] * (min_items - len(parts)))
>    return parts
>
> Use would be like this:
>
> a, b, c, d = "1,2,3".split(',', None, 4)
>
> Probably not a great idea, but I'm tossing it out there, anyway.

This is not a common thing to do, and it is easy enough to implement
in a single assignment even without a helper function:

a, b, c, d = ("1,2,3".split(',', 4) + [None] * 4)[:4]

This also has the advantage of giving you explicit control of the
filler value for missing pieces.

(Note: be careful not to use a _mutable_ filler value in this manner!)

- Tal



More information about the Python-ideas mailing list