I'm wondering if collections.Iterable should inherit from
collections.Container"?
In Python, anything that supports __iter__ automatically supports tests using
the "in" operator:
class A:
def __iter__(self):
for i in (1,2,3):
yield i
>>> 2 in A()
True
The two concepts are deeply related. Anywhere we can write "for x in s: ..."
we can also write "if x in s: ...".
The new definition of Iterable would look like this:
class Iterable(Container):
__metaclass__ = ABCMeta
@abstractmethod
def __iter__(self):
while False:
yield None
@classmethod
def __subclasshook__(cls, C):
if cls is Iterable:
if any("__iter__" in B.__dict__ for B in C.__mro__):
return True
return NotImplemented
def __contains__(self, value):
for v in self:
if v == value:
return True
return False
Raymond
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