roy at panix
Jul 3, 2008, 7:26 PM
Post #4 of 4
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In article <luc0k5-spf.ln1 [at] lairds>, claird [at] lairds (Cameron Laird)
wrote:
> In article <mailman.37.1215119171.20628.python-list [at] python>,
> Matthew Fitzgibbons <elessar [at] nienna> wrote:
> >Alexnb wrote:
> >> Okay this is a simple question I just don't know how. If I have a list,
> >> say:
> >>
> >> funList = []
> >>
> >> and after a while something possible should have been appended to it, but
> >> wasn't. How can I test if that list is empty.
> >
> >if not funList:
> > do_something()
> .
> .
> .
> It's also perfectly legitimate--and arguably even more
> precise--to write
>
> if funList == []:
> do_something()
Any of these will be true for an empty list and false for a non-empty list:
not funList
len(funList) == 0
funList == []
Where they differ is how they behave for values of funList which are not
lists. For example, if you did funList = (), then the first two would be
true and the last one false. If you did funList = 0, the first and last
would be true, and the middle one would raise an exception.
The point is that if you're *sure* the item in question is going to be a
list, then any of them are pretty much as good as any other. If it's a
parameter that's being passed into a routine, so you can't be sure what
type it is, then you should be thinking a little harder about how flexible
you want to be.
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