why do we need np.squeeze()?

Question

Very often, arrays are squeezed with np.squeeze(). In the documentation, it says

Remove single-dimensional entries from the shape of a.

Answer 1

One example of the importance is when multiplying arrays. Two 2-dimensional arrays will multiply each value at a time

e.g.

>>> x = np.ones((2, 1))*2
>>> y = np.ones((2, 1))*3
>>> x.shape
(2,1)
>>> x*y
array([[ 6.],
       [ 6.]])

If you multiply a 1d array by a 2d array then the behaviour is different

>>> z = np.ones((2,))*3
>>> x*z
array([[ 6.,  6.],
       [ 6.,  6.]])

Secondly, you also might want to squeeze the earlier dimensions e.g. a.shape = (1,2,2) to a.shape = (2,2)