Question

I probably didn’t ask correctly: I would like a list value that can match any list: the “inverse” of (None,)
but even with (None,) it will match item as None (which I don’t want)

The point is I have a function working with: [x for x in my_list if x[field] not in filter_list]

and I would like to filter everything or nothing without making tests like:
if filter_list==(None,): return [] and if filter_list==('*',): return my_list

PS: I wanted to simplify my question leading to some errors (list identifier) or stupid thing [x for x in x] 😉

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Hi,

I need to do some filtering with list comprehension in python.

if I do something like that:

[x for x in list if x in (None,)]

I get rid of all values, which is fine

but I would like to have the same thing to match everything

I can do something like:

[x for x in list if x not in (None,)]

but it won’t be homogeneous with the rest

I tried some things but for example (True,) matches only 1

Note than the values to filter are numeric, but if you have something generic (like (None,) to match nothing), it would be great

Thanks
Louis

Answer 1

__contains__ is the magic method that checks if something is in a sequence:

class everything(object):
    def __contains__(self, _):
        return True           

for x in (1,2,3):
    print x in everything()