# [Numpy-discussion] bug in reshape ?

josef.pktd@gmai... josef.pktd@gmai...
Tue Nov 22 18:45:37 CST 2011

```might be an old story >>> np.__version__  -> '1.5.1'

It thought for once it's easier to use reshape to add a new axis
but my results got weird (normal(0,1) sample of 2.13795875e-314)

>>> x = 1
>>> y = np.arange(3)
>>> z = np.arange(2)[:,None]
[array([[1, 1, 1],
[1, 1, 1]]), array([[0, 1, 2],
[0, 1, 2]]), array([[0, 0, 0],
[1, 1, 1]])]
>>> x1, y1, z1 = np.broadcast_arrays(x,y,z)
>>> map(np.shape, (x1, y1, z1))
[(2, 3), (2, 3), (2, 3)]

shape looks fine, let's add an extra axis with reshape

>>> x1.reshape(2,3,1)
array([[[          1],
[          1],
[ 1099464714]],

[[-2147481592],
[        184],
[          1]]])

what's that ?

>>> (0+x1).reshape(2,3,1)
array([[[1],
[1],
[1]],

[[1],
[1],
[1]]])

>>> (y1*1.).reshape(2,3,1)
array([[[ 0.],
[ 1.],
[ 2.]],

[[ 0.],
[ 1.],
[ 2.]]])

>>> (y1).reshape(2,3,1)
array([[[          0],
[          1],
[          2]],

[[          0],
[ 1099447643],
[-2147483648]]])

>>> x1, y1, z1 = np.broadcast_arrays(x,y,z)
>>> x1[...,None]
array([[[1],
[1],
[1]],

[[1],
[1],
[1]]])

>>> x1.shape
(2, 3)
>>> x1.reshape(2,3,1)
array([[[          1],
[          1],
[ 1099464730]],

[[-2147479536],
[ -445054780],
[ 1063686842]]])

the background story: playing broadcasting tricks for
http://projects.scipy.org/scipy/ticket/1544

Josef
```