how to get the index of numpy.random.choice? - python

Question

Is it possible to modify the numpy.random.choice function in order to make it return the index of the chosen element? Basically, I want to create a list and select elements ran

Answer 1

numpy.random.choice(a, size=however_many, replace=False)

If you want a sample without replacement, just ask numpy to make you one. Don't loop and draw items repeatedly. That'll produce bloated code and horrible performance.

Example:

>>> a = numpy.arange(10)
>>> a
array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
>>> numpy.random.choice(a, size=5, replace=False)
array([7, 5, 8, 6, 2])

On a sufficiently recent NumPy (at least 1.17), you should use the new randomness API, which fixes a longstanding performance issue where the old API's replace=False code path unnecessarily generated a complete permutation of the input under the hood:

rng = numpy.random.default_rng()
result = rng.choice(a, size=however_many, replace=False)