AttributeError: module 'numpy' has no attribute 'flip'

np.flip has been introduced for versions v.1.12.0 and beyond. For older versions, you can consider using np.fliplr and np.flipud.

Alternatively, upgrade your numpy version using pip install --user --upgrade numpy.

Yes,flip is new, but there isn't anything magical about it. Here's the code:

def flip(m, axis):
    if not hasattr(m, 'ndim'):
        m = asarray(m)
    indexer = [slice(None)] * m.ndim
    try:
        indexer[axis] = slice(None, None, -1)
    except IndexError:
        raise ValueError("axis=%i is invalid for the %i-dimensional input array"
                         % (axis, m.ndim))
    return m[tuple(indexer)]

The essence of the action is that it indexes your array with one or more instances of ::-1 (the slice(None,None,-1)). flipud/lr do the same thing.

With this x, flip does:

In [826]: np.array([1,2,3])[::-1]
Out[826]: array([3, 2, 1])