Python3 doc, operator reflection

[Johannes Bauer]

Hi group,

in http://docs.python.org/3/reference/datamodel.html#customization the
doc reads:

There are no swapped-argument versions of these methods (to be used when the left argument does not support the operation but the right argument does); rather, __lt__() and __gt__() are each other’s reflection, __le__() and __ge__() are each other’s reflection, and __eq__() and __ne__() are their own reflection.

But shouldn't __lt__ be the reflection or __ge__ and __gt__ the
reflection of __le__?

Best regards,
Johannes

 

[Chris Angelico]

But shouldn't __lt__ be the reflection or __ge__ and __gt__ the
reflection of __le__?

lt is the negation of ge, but it's the reflection of gt. Consider this:

1 < 2
2 > 1

If Python can't ask 1 if it's less than 2, it'll ask 2 if it's greater than1.

ChrisA

 

[Johannes Bauer]

Am 28.10.2013 13:23, schrieb Chris Angelico:

lt is the negation of ge, but it's the reflection of gt. Consider this:

1 < 2
2 > 1

If Python can't ask 1 if it's less than 2, it'll ask 2 if it's greater than 1.

Ah, I see. Thanks for clearing that up!

Best regards,
Joe

 

[random832]

Hi group,

in http://docs.python.org/3/reference/datamodel.html#customization the
doc reads:


But shouldn't __lt__ be the reflection or __ge__ and __gt__ the
reflection of __le__?

No... a < b is b > a - you're thinking of the relationship between a < b
and not(a >= b), which is not the argument-swapping it is referring to.