Why Do Methods Of Classes That Inherit From Numpy Arrays Return Different Things?

Let's look at some very simple behaviour of numpy arrays: import numpy as np arr = np.array([1,2,3,4,5]) max_value = arr.max() # returns 5 Now I create a class which inherits from

Solution 1:

Following the numpy docs: array_wrap gets called at the end of numpy ufuncs and other numpy functions, to allow a subclass to set the type of the return value and update attributes and metadata.

class CustomArray(np.ndarray):
    def __new__(cls, a, dtype=None, order=None):
        obj = np.asarray(a, dtype, order).view(cls)
        return obj

    def __array_wrap__(self, out_arr, context=None):
        return np.ndarray.__array_wrap__(self, out_arr, context)

c = CustomArray([1,2,3,4])
c.max() # returns 4