What does __contains__ do, what can call __contains__ function
to get your code to do something (although nothing useful):
class a(object):
d = 'ddd'
def __contains__(self, m):
if self.d:
return True
b = a()
>>> 'd' in b
True
The docs.
Like all special methods (with "magic names" that begin and end in __
), __contains__
is not meant to be called directly (except in very specific cases, such as up=calls to the superclass): rather, such methods are called as part of the operation of built-ins and operators. In the case of __contains__
, the operator in question is in
-- the "containment check" operator.
With your class a
as you present it (except for fixing your typo, and using True
instead of true
!-), and b
as its instance, print 'x' in b
will print True
-- and so will any other containment check on b
, since b
always returns True
(because self.d
, a non-empty string, is true).