18 Jul
2017
18 Jul
'17
3:37 p.m.
When using ndarray.squeeze, a view is returned, which means you can do the follow (somewhat-contrived) operation:
def fill_contrived(a):
a.squeeze()[...] = 2 return a
fill_contrived(np.array([1]))
array(2)
However, when tried with a masked array, this can fail, breaking liskov subsitution:
fill_contrived(np.ma.array([1], mask=[True]))
MaskError: Cannot alter the masked element.
This fails because squeeze breaks the contract of returning a view, instead deciding sometimes to return masked.
There is a patch that fixes this in gh-9432 https://github.com/numpy/numpy/pull/9432 - however, by necessity it breaks any existing code that uses m_arr.squeeze() is np.ma.masked.
Is this too breaking a change?
Eric