Behavior when 0, 1, False, True is used for the dictionary (dict) key

A Hashable object can be used for the Python dictionary (dict) key, and the hash value is used as the key. Python's bool type is implemented as a subclass of the ʻint type, where Falsehas the same hash value as0 and Truehas the same hash value as1`.

>>> hash(0)
0
>>> hash(False)
0
>>> hash(1)
1
>>> hash(True)
1

Now let's see what happens when we use 0, 1, False, True as dictionary keys.

>>> d = { 0: 'zero', True: 'true' }
>>> d
{0: 'zero', True: 'true'}
>>> d[0]
'zero'
>>> d[True]
'true'
>>> d[False]
'zero'
>>> d[1]
'true'

I also got False and 1 which are not in the dictionary. Since the hash values are the same, it is a natural behavior.

Let's assign it to the dictionary.

>>> d
{0: 'zero', True: 'true'}
>>> d[False] = 'false'
>>> d[1] = 'one'
>>> d
{0: 'false', True: 'one'}

The key remains 0 and True, and the values have been updated to 'false' and 'one'.

It turns out that the key uses the value from the first assignment and the value is the last assigned value. Not surprisingly, it was an interesting result.

>>> d = { 0: 'zero', True: 'true', 1: 'one', False: 'false'}
>>> d
{0: 'false', True: 'one'}