[Numpy-discussion] random.RandomState and deepcopy

Neal Becker ndbecker2 at gmail.com
Fri Mar 13 13:59:56 EDT 2015

Robert Kern wrote:

> On Fri, Mar 13, 2015 at 5:34 PM, Neal Becker <ndbecker2 at gmail.com> wrote:
>> It is common that to guarantee good statistical independence between
> various
>> random generators, a singleton instance of an RNG is shared between them.
>> So I typically have various random generator objects, which (sometimes
>> several levels objects deep) embed an instance of RandomState.
>> Now I have a requirement to copy a generator object (without knowing
> exactly
>> what that generator object is).
> Or rather, you want the generator object to *avoid* copies by returning
> itself when a copy is requested of it.
>> My solution is to use deepcopy on the top-level object.  But I need to
>> overload __deepcopy__ on the singleton RandomState object.
>> Unfortunately, RandomState doesn't allow customization of __deepcopy__
>> (or
>> anything else).  And it has no __dict__.
> You can always subclass RandomState to override its __deepcopy__.
> --
> Robert Kern

Yes, I think I prefer this:

from numpy.random import RandomState

class shared_random_state (RandomState):
    def __init__ (self, rs):
        RandomState.__init__(self, rs)

    def __deepcopy__ (self, memo):
        return self

Although, that means I have to use it like this:

rs = shared_random_state (0)

where I really would prefer (for aesthetic reasons):

rs = shared_random_state (RandomState(0))

but I don't know how to do that if shared_random_state inherits from 

Those who fail to understand recursion are doomed to repeat it

More information about the NumPy-Discussion mailing list