Pretty rare but not unheard of. I do know that most of the code bases I work in would require significant reworking if I have to expect `==` to throw a TypeError for basic builtin types.
Re:The Python Unicode Mess
by guitarbill on Saturday October 06, 2018 @04:57PM
(#18157225)
Not quite with ==, but there is precedence where operators with basic builtin types throw a TypeError when the operation doesn't make sense:
>>> 0 > None
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: '>' not supported between instances of 'int' and 'NoneType'
Re:The Python Unicode Mess
by wool_gather on Saturday October 06, 2018 @05:51PM
(#18157457)
Absolutely; there's no good boolean answer for > when you have different types, so the `TypeError` is perfect there.
Re:The Python Unicode Mess
by ubernostrum on Saturday October 06, 2018 @11:58PM
(#18158776)
At the same time, this result is entirely dependent on the types involved. For example, "1.0 > 0" has a well-defined answer, and Python returns it.
Considering the expression "x > y", the full process is:
1. Call x.__gt__(y).
2. If that returns a bool, that's the result. If it raises an exception, propagate the exception.
3. If it returns the sentinel value NotImplemented, attempt the reflected version of the operation: y.__lt__(x).
4. If that returns a bool, that's the result. If it raises an exception, propagate the exception.
5. If it returns the sentinel value NotImplemented, raise TypeError and inform the programmer this operator is not valid on these types.
Could you explain how your example shows that?
Which “that”? If you’re asking about `OrderedDict`, I’m referring to equality between `OrderedDict`s:
>>> a = OrderedDict([(1, 2), (3, 4)])
>>> b = {1: 2, 3: 4}
>>> c = OrderedDict(reversed(a.items()))
>>> a == b == c
True
>>> a == c
FalseI was referring to this:
> Also, `==` doesn’t always answer the question of whether two things are equivalent
because the examples you posteda kinda make it look like it does, i.e. `1.0 == 1` even though one is a float and the other is an int.
Also, `==` doesn’t always answer the question of whether two things are equivalent in Python:
(OrderedDict equality isn’t transitive.)