Python: double nested list comprehension

Question

I'm writing a function that samples inputs to another numerical function that has 5 inputs, with given min and max values for each input. It should result in num_samples^5 different input combinations.

I would like to make this piece of code shorter such that the explicit indices 0 to 4 are not needed anymore.

num_inputs = 5
num_samples = 10.0

sampled_inputs = [[a, b, c, d, e]
                  for a in sample_range(mins[0], maxes[0], num_samples)
                  for b in sample_range(mins[1], maxes[1], num_samples)
                  for c in sample_range(mins[2], maxes[2], num_samples)
                  for d in sample_range(mins[3], maxes[3], num_samples)
                  for e in sample_range(mins[4], maxes[4], num_samples)]

where sample_range is a function that samples num_samples numbers between min and max.

Is there any trick I'm not seeing yet? Thanks in advance.

Joshua Fox · Accepted Answer · 2020-02-13 08:09:59Z

1

Are you trying to get a cartesian product here?

If so, use itertools.product.

import itertools
lists = [sample_range(mins[i], maxes[i], num_samples) for i in range(4)]
prod = itertools.product(*lists)
for elem in prod:
   print(elem)

edited Feb 13, 2020 at 8:09

answered Feb 13, 2020 at 8:01

Joshua Fox

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1 Comment

Fabian Over a year ago

Thank you, yes, after thinking about it, it is a cartesian product.

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