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 a

Answer 1

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]

Answer 2

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.)