How and where to use Python's and, or, invert magic methods properly

Question

I was googling around to find any use cases or examples of these methods but could not find any detailed explanation, they are just listed along other similar methods. Actually, I was looking through some code on github and came across these methods but could not understand the usage. Can somebody please provide a detailed explanation of these methods. This is the link of github code where I came across them: https://github.com/msiemens/tinydb/blob/master/tinydb/queries.py

score 7 · Accepted Answer · edited Sep 27 '17 at 05:56

The magic methods __and__, __or__ and __invert__ are used to override the operators a & b, a | b and ~a respectively. That is, if we have a class

class QueryImpl(object):
    def __and__(self, other):
        return ...

then

a = QueryImpl(...)
b = QueryImpl(...)
c = a & b

is equivalent to

a = QueryImpl(...)
b = QueryImpl(...)
c = a.__and__(b)

These methods are overridden in tinydb to support this syntax:

>>> db.find(where('field1').exists() & where('field2') == 5)
>>> db.find(where('field1').exists() | where('field2') == 5)
#                                    ^

How and where to use Python's __and__, __or__, __invert__ magic methods properly

1 Answers1

How and where to use Python's and, or, invert magic methods properly