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

Question

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?

Now we will see solution for issue: How to check if an object is a list or tuple (but not string)?

Answer

In python 2 only (not python 3):

assert not isinstance(lst, basestring)

Is actually what you want, otherwise you’ll miss out on a lot of things which act like lists, but aren’t subclasses of list or tuple.

This question is answered By – Nick Craig-Wood

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