Is it possible to overload logical and in Python?

Question

I was under the impression it was possible to overload and in Python, but reading through the docs just now, I realized that __and__ refers to the bitwise & operator, not logical and.

Am I overlooking something, or is it not possible to overload logical and in Python?

I'm curious: what would you like to make an overloaded and do? Or are you just asking for purely theoretical reasons? — PM 2Ring
– PM 2Ring, Commented Aug 31, 2015 at 12:53
Purely theoretical. I'm writing something that needs to work with Python AST. For most things like Add, I replace it with a call to __add__, but I was surprised that I couldn't find a function to replace an And node in AST with. — ArtOfWarfare
– ArtOfWarfare, Commented Aug 31, 2015 at 12:59
I don’t see a good reason why you would want to introduce custom behavior for logical operators that does not match the behavior from evaluating __bool__. — poke
– poke, Commented Aug 31, 2015 at 13:03

Salailah · Accepted Answer · 2015-08-31 12:55:45Z

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No this is not possible. There is a proposal that adds this functionality but for now, it is rejected.

answered Aug 31, 2015 at 12:55

Salailah

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Community · Accepted Answer · 2017-05-23 11:52:09Z

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No, it is not possible. See here.

edited May 23, 2017 at 11:52

CommunityBot

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answered Aug 31, 2015 at 12:45

rkrzr

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2 Comments

ArtOfWarfare Over a year ago

Hm. is makes some sense to me, but I'm surprised that and and or cannot be overloaded.

rkrzr Over a year ago

Yes, it is indeed a limitation of the language. But you can override the bitwise operators & and | , as you noticed. This is used by e.g. SQLAlchemy and you can also use it yourself of course.

Juuso Meriläinen · Accepted Answer · 2015-08-31 12:49:02Z

There is no straight way to do this. You could override __nonzero__ for your objects to modify their truth value.

class Truth: def __init__(self, truth): self.truth = truth def __nonzero__(self): return self.truth t = Truth(True) f = Truth(False) print bool(t and t) print bool(t and f) print bool(f and f)

Compatibility tip: __nonzero__ has been renamed to __bool__ in 3.X.

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