numpy array indexing: list index and np.array index give different result

Question

I am trying to index an np.array using list and np.array indexes. But they give different result.

Here is an illustration:

import numpy         


        

Answer 1

From numpy indexing documentation:

ndarrays can be indexed using the standard Python x[obj] syntax, where x is the array and obj the selection.

...
Basic slicing occurs when obj is a slice object (constructed by start:stop:step notation inside of brackets), an integer, or a tuple of slice objects and integers. Ellipsis and newaxis objects can be interspersed with these as well. In order to remain backward compatible with a common usage in Numeric, basic slicing is also initiated if the selection object is any non-ndarray sequence (such as a list) containing slice objects, the Ellipsis object, or the newaxis object, but not for integer arrays or other embedded sequences. ...