How to check if an object is a list or tuple (but not string)?

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This is what I normally do in order to ascertain that the input is a list/tuple – but not a str. Because many times I stumbled upon bugs where a function passes a str object by mistake, and the target function does for x in lst assuming that lst is actually a list or tuple.

assert isinstance(lst, (list, tuple))

My question is: is there a better way of achieving this?

19 Answers
19

Python 3:

import collections.abc

if isinstance(obj, collections.abc.Sequence) and not isinstance(obj, str):
    print("`obj` is a sequence (list, tuple, etc) but not a string or a dictionary.")

Changed in version 3.3: Moved global namespace of “Collections Abstract Base Classes” from abc to collections.abc module. For backwards compatibility, they will continue to be visible in this module as well until version 3.8 where it will stop working.

Python 2:

import collections

if isinstance(obj, collections.Sequence) and not isinstance(obj, basestring):
    print "`obj` is a sequence (list, tuple, etc) but not a string or unicode or dictionary."

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