numpy.all(a, axis=None, out=None)

Test whether all array elements along a given axis evaluate to True.

Parameters :

a : array_like

Input array or object that can be converted to an array.

axis : int, optional

Axis along which a logical AND is performed. The default (axis = None) is to perform a logical AND over a flattened input array. axis may be negative, in which case it counts from the last to the first axis.

out : ndarray, optional

Alternate output array in which to place the result. It must have the same shape as the expected output and its type is preserved (e.g., if dtype(out) is float, the result will consist of 0.0’s and 1.0’s). See doc.ufuncs (Section “Output arguments”) for more details.

Returns :

all : ndarray, bool

A new boolean or array is returned unless out is specified, in which case a reference to out is returned.

See also

equivalent method
Test whether any element along a given axis evaluates to True.


Not a Number (NaN), positive infinity and negative infinity evaluate to True because these are not equal to zero.


>>> np.all([[True,False],[True,True]])
>>> np.all([[True,False],[True,True]], axis=0)
array([ True, False], dtype=bool)
>>> np.all([-1, 4, 5])
>>> np.all([1.0, np.nan])
>>> o=np.array([False])
>>> z=np.all([-1, 4, 5], out=o)
>>> id(z), id(o), z                             
(28293632, 28293632, array([ True], dtype=bool))

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