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.