Can I use ~A to invert a numpy array of booleans, instead of the rather awkward functions np.logical_and() and np.invert()?
Indeed, ~ seems to work fine, but I can't find it in any nympy reference manual, and - more alarmingly - it certainly does not work with scalars (e.g. bool(~True) returns True !), so I'm a little bit worried ...
short answer: YES
Ref:
http://docs.scipy.org/doc/numpy/reference/generated/numpy.invert.html
Notice:
Computes the bit-wise NOT of the underlying binary representation of the integers in the input arrays. This ufunc implements the C/Python operator ~.
and
bitwise_not is an alias for invert:
>> np.bitwise_not is np.invert
>> True
boolean not and logic not are always different. Both the question and the answer are about boolean not. Thanks for reminding anyway.
dtype=bool. I just stumbled upon the edge case of an array full of True and False objects with dtype=object. These are converted like ~True => -2 and ~False => -1. See the duplicate target linked in the question comments.You can use the tilde if the array's dtype is boolean and you are sure that this won't change as the software matures. However, np.logical_not has two advantages:
np.nans or other objects make it into your array.There is also np.invert but it doesn't work with object arrays and the word is ambiguous.
~np.array([False, True], dtype=bool)
Out[7]: array([ True, False])
~np.array([False, True], dtype=object)
Out[9]: array([-1, -2], dtype=object)
np.invert([True, False])
Out[4]: array([False, True])
np.invert((np.array([True, False], dtype=object)))
Out[5]: array([-2, -1], dtype=object)
np.logical_not(np.array([False, True], dtype=bool))
Out[8]: array([ True, False])
np.logical_not(np.array([False, True], dtype=object))
Out[10]: array([True, False], dtype=object)