On 5/29/2013 1:46 PM, Croepha wrote:
Is there anything like this in the standard library?
class AnyFactory(object):
def __init__(self, anything):
self.product = anything
def __call__(self):
return self.product
def __repr__(self):
return "%s.%s(%r)" % (self.__class__.__module__,
self.__class__.__name__, self.product)
my use case is:
collections.defaultdict(AnyFactory(collections.defaultdict(AnyFactory(None))))
And I think lambda expressions are not preferable...
It's not clear to me that this does what you want. Won't your
defaultdict use the same defaultdict for all of its default values? This
is hard to describe in English but:
d =
collections.defaultdict(AnyFactory(collections.defaultdict(AnyFactory(None))))
d[1][1] = 1
d[2][2] = 2
print d[1]
#-> defaultdict(__main__.AnyFactory(None), {1: 1, 2: 2})
print d[1] is d[2]
#-> True
It might not be possible to get this right without lambdas:
d = collections.defaultdict(lambda: collections.defaultdict(lambda: None))
d[1][1] = 1
d[2][2] = 2
print d[1]
#-> defaultdict(<function <lambda> at 0x02091D70>, {1: 1})
print d[1] is d[2]
#-> False
--Ned.
I found itertools.repeat(anything).next and
functools.partial(copy.copy, anything)
but both of those don't repr well... and are confusing...
I think AnyFactory is the most readable, but is confusing if the
reader doesn't know what it is, am I missing a standard implementation
of this?
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