Test if numpy array contains only zeros

The other answers posted here will work, but the clearest and most efficient function to use is numpy.any():

>>> all_zeros = not np.any(a)

or

>>> all_zeros = not a.any()

• This is preferred over numpy.all(a==0) because it uses less RAM. (It does not require the temporary array created by the a==0 term.)
• Also, it is faster than numpy.count_nonzero(a) because it can return immediately when the first nonzero element has been found.
  • Edit: As @Rachel pointed out in the comments, np.any() no longer uses "short-circuit" logic, so you won't see a speed benefit for small arrays.

Check out numpy.count_nonzero.

>>> np.count_nonzero(np.eye(4))
4
>>> np.count_nonzero([[0,1,7,0,0],[3,0,0,2,19]])
5

I'd use np.all here, if you have an array a:

>>> np.all(a==0)