Python overload object.and method

Question

I'm writing a class and want to overload the __and__ function

class Book(object):
    def __init__(self, name, pages):
        self.name = name
        self.pages = pages

    def __and__(self, other):
        return '{}, {}'.format(self.name, other.name)

When I run this

Book('hamlet', 50) and Book('macbeth', 60)

I would expect to get 'hamlet, macbeth'

However, it appears the overload does nothing. What am I doing wrong?

score 4 · Answer 1 · edited May 23 '17 at 11:47

4

The __and__ method is an override for the and operator &:

>>> Book('hamlet', 50) & Book('macbeth', 60)
'hamlet, macbeth'

Sadly, you can not override the and operator.

edited May 23 '17 at 11:47

Community

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answered May 10 '17 at 11:37

Wander Nauta

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But you could override `__bool__ / __nonzero__` – timgeb May 10 '17 at 11:39
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@timgeb That wouldn't help do what the OP is trying to do. – khelwood May 10 '17 at 11:40
@khelwood of course not, I just mentioned this for completeness. – timgeb May 10 '17 at 11:40

Cory Kramer · Answer 2 · 2017-05-10T12:07:58.827

3

The __and__ method is actually grouped with the numeric type methods, therefore it does not represent logical and (which is the and keyword) but rather the & operator

>>> Book('hamlet', 50) & Book('macbeth', 60)
'hamlet, macbeth'

edited May 10 '17 at 12:07

answered May 10 '17 at 11:37

Cory Kramer

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Python overload object.__and__ method

2 Answers2

Python overload object.and method