[Numpy-discussion] Equality not working as expected with ndarray sub-class

Thomas Robitaille thomas.robitaille at gmail.com
Thu Jul 4 09:06:49 EDT 2013

Hi everyone,

The following example:

    import numpy as np

    class SimpleArray(np.ndarray):

        __array_priority__ = 10000

        def __new__(cls, input_array, info=None):
            return np.asarray(input_array).view(cls)

        def __eq__(self, other):
            return False

    a = SimpleArray(10)
    print (np.int64(10) == a)
    print (a == np.int64(10))

gives the following output

    $ python2.7 eq.py

so that in the first case, SimpleArray.__eq__ is not called. Is this a
bug, and if so, can anyone think of a workaround? If this is expected
behavior, how do I ensure SimpleArray.__eq__ gets called in both


ps: cross-posting to stackoverflow

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