Andrey Fedorov wrote:
It may be intuitive to you, but its not true, written down
anywhere, nor assumed by the language, and the mathematical
meaning of the operators doesn't matter to Python. Python
purposefully does not enforce anything for these methods.
Right, so neither is anything in PEP-8, but it's still considered
"good practice". I'm running across examples like you gave (__sub__
having a side-effect on the left-hand operand) in some code, and am
trying to find concrete justification for avoiding it.
- Andrey
This is all about communication. Python allows you to call a cat a dog.
You'll confuse everyone if you do so, but you can do it.
If your '-' operator is doing something else than returning the sub
result, it's your call, but do not expect people to get it easily. You'd
better be good at writting the documentation :-)
JM
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