python - Is there a way to check if NumPy arrays share the same data?

Question

My impression is that in NumPy, two arrays can share the same memory. Take the following example:

import numpy as np
a=np.arange(27)
b=a.reshape((3,3,3))
a[0]=5000
print (b[0,0,0]) #5000

#Some tests:
a.data is b.data #False
a.data == b.data #True

c=np.arange(27)
c[0]=5000
a.data == c.data #True ( Same data, not same memory storage ), False positive

So clearly b didn't make a copy of a; it just created some new meta-data and attached it to the same memory buffer that a is using. Is there a way to check if two arrays reference the same memory buffer?

My first impression was to use a.data is b.data, but that returns false. I can do a.data == b.data which returns True, but I don't think that checks to make sure a and b share the same memory buffer, only that the block of memory referenced by a and the one referenced by b have the same bytes.

Answer 1

You can use the base attribute to check if an array shares the memory with another array:

>>> import numpy as np
>>> a = np.arange(27)
>>> b = a.reshape((3,3,3))
>>> b.base is a
True
>>> a.base is b
False

Not sure if that solves your problem. The base attribute will be None if the array owns its own memory. Note that an array's base will be another array, even if it is a subset:

>>> c = a[2:]
>>> c.base is a
True