[Solved] Why do keys() and items() methods return different Boolean values for same key? (Python 3.6) [closed]

Question

items() contains tuples, key-value pairs:

>>> spam.items()
dict_items([('name', 'Zophie'), ('age', 7)])

Your key is not such a tuple. It may be contained in one of the tuples, but in does not test for containment recursively.

Either test for the correct key-value tuple:

>>> ('name', 'Zophie') in spam.items()
True

or if you can’t get access to just the keys() dictionary view, use the any() function to test each pair individually (iteration is halted early when a match is found):

>>> any('name' in pair for pair in spam.items())
True

or

>>> any(key == 'name' for key, value in spam.items())
True

On a separate note, if all you are doing is testing for a key, then just use key in dictionary. There is no need to create a separate dictionary view over the keys for that case; it’s just a waste of Python cycles and memory as containment testing against the dictionary achieves the exact same result.

Accepted Answer

items() contains tuples, key-value pairs:

>>> spam.items()
dict_items([('name', 'Zophie'), ('age', 7)])

Your key is not such a tuple. It may be contained in one of the tuples, but in does not test for containment recursively.

Either test for the correct key-value tuple:

>>> ('name', 'Zophie') in spam.items()
True

or if you can’t get access to just the keys() dictionary view, use the any() function to test each pair individually (iteration is halted early when a match is found):

>>> any('name' in pair for pair in spam.items())
True

or

>>> any(key == 'name' for key, value in spam.items())
True

On a separate note, if all you are doing is testing for a key, then just use key in dictionary. There is no need to create a separate dictionary view over the keys for that case; it’s just a waste of Python cycles and memory as containment testing against the dictionary achieves the exact same result.