Python: check if an object is a sequence

Question

In python is there an easy way to tell if something is not a sequence? I tried to just do: if x is not sequence but python did not like that

Answer 1

For Python 3 and 2.6+, you can check if it's a subclass of collections.Sequence:

>>> import collections
>>> isinstance(myObject, collections.Sequence)
True

In Python 3.7 you must use collections.abc.Sequence (collections.Sequence will be removed in Python 3.8):

>>> import collections.abc
>>> isinstance(myObject, collections.abc.Sequence)
True

However, this won't work for duck-typed sequences which implement __len__() and __getitem__() but do not (as they should) subclass collections.Sequence. But it will work for all the built-in Python sequence types: lists, tuples, strings, etc.

While all sequences are iterables, not all iterables are sequences (for example, sets and dictionaries are iterable but not sequences). Checking hasattr(type(obj), '__iter__') will return True for dictionaries and sets.

Answer 2

The Python 2.6.5 documentation describes the following sequence types: string, Unicode string, list, tuple, buffer, and xrange.

def isSequence(obj):
    return type(obj) in [str, unicode, list, tuple, buffer, xrange]