了解numpy的any函数

Question

I came across a function named any with numpy and I could not understand its usage in some context which is given as folllows:

if np.subtract(original.shape, duplicate.shape).any():
   # Do something
else:
   # Carry on with the usual tasks

Could someone help me understand what is happening here? What is being checked? The documentation says,

Tests whether any array element along a given axis evaluates to True.

Is it being checked for equality? To understand this better, how could I rewrite the any call?

Answer 1

It's being checked for "True"ness.

Try this:

import numpy

print(numpy.any([0, 0, 0, 0, 0]))
print(numpy.any([0, 0, 0, 0, 1]))

Answer 2

np.any(x) checks if any of the elements in x is true. In your case, it checks if the arrays original and duplicate have at least a different dimension.

You could rewrite this as:

res = False
for so, sd in zip(original.shape, duplicate.shape):
    if so != sd:
        res = True

if res:
    # Do something
else:
   # Carry on with the usual tasks

Answer 3

The any method checks if at least on element in the given data is evaluated as True .

In python the following things are evaluated False :

• None
• False
• any numeric zero
• empty strings, sets, lists, dictionaries ...
• anything that has a __len__ method which returns 0 or a __bool__ method that returns False

Everything else is evaluated True .

If the data checked by the any method contains at least one item that does not meet these requirements, it returns True else False