TypeError when indexing a list with a NumPy array: only integer scalar arrays can be converted to a scalar index

Question

The following code:

x = list(range(0,10))
random.shuffle(x)
ind = np.argsort(x)
x[ind]

produces the error: TypeError: only integer scalar arrays can be converted to a scalar index

Note that my problem is different than in the question, "numpy array TypeError: only integer scalar arrays can be converted to a scalar index", which is attempting something more complex.

My mistake in this question is that I'm trying to use a list of indexes on an ordinary python list -- see my answer. I expect it happens much more broadly than just with using range and shuffle.

Answer 1

The problem is that I am attempting to index x, an ordinary Python list, as if it were a numpy array. To fix it, simply convert x to a numpy array:

x = list(range(0,10))
random.shuffle(x)
ind = np.argsort(x)
x = np.array(x) # This is the key line
x[ind]

(This has happened to me twice now.)

Answer 2

Good answer - but I would add that if the list cannot be converted to a numpy array (i.e. you have a list of string) you cannot slice it with an array of indices as described above. The most straightforward alternative is

[x[i] for i in ind]