Mark Dickinson <[email protected]> added the comment:
It's documented here:
https://docs.python.org/3/library/stdtypes.html#mapping-types-dict
> Numeric types used for keys obey the normal rules for numeric
> comparison: if two numbers compare equal (such as 1 and 1.0) then
> they can be used interchangeably to index the same dictionary entry.
Since False == 0, False and 0 are interchangeable as dictionary keys. Similarly
for True and 1. Note that the dictionary you created only actually has two
entries:
>>> dta = {False: 'false', True: 'true', 0: 'zero', 1: 'one'}
>>> dta
{False: 'zero', True: 'one'}
Though calling out numeric types in particular in the docs does feel a little
odd to me: the rule is that *any* two hashable objects that compare equal
should be interchangeable for the purposes of dictionary lookup (or set
membership, come to that). There's nothing particularly special about numbers
in this context.
----------
nosy: +mark.dickinson
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<https://bugs.python.org/issue33572>
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