numpy array subclass unexpedly shares attributes across instances

Question

I am having a weird subclass numpy.ndarray issue that feels like
Values of instance variables of superclass persist across instances of subclass
But I have not been

Answer 1

The problem is here:

def __new__(cls, input_array, attrs={})

Never do this attrs={} in a function header. The expected result is (probably) not what you think it is. This is a common Python Pitfall. See here Default Parameter Values in Python

The right way how to do this:

def __new__(cls, input_array, attrs=None):
    if attrs is None:
        attrs = {}