All combinations from dictionary of lists

Question

Problem definition:

• I have a dictionary with N > 0 parameter lists as values and parameter names as keys.
• Each of the lists may be of a different length (e.g., k > 0, l > 0, m > 0...).
• My goal is to produce a unified list of tuples [(a11, a21, a31, ...), (a12, a22, a32, ...), ..., (a1k, a2l, a3m, ...)], where each tuple is a set of length N, and containing corresponding parameter values.

Example:

Given the following parameter dictionary:

const_params_dict= dict(a=[-1, 1], b=[-5, -4, -3, -2, -1, 1, 2, 3, 4, 5], th=[0.5])

the desired output will be:

Out: [(-1, -5, 0.5), (-1, -4, 0.5), (-1, -3, 0.5), (-1, -2, 0.5), ..., (-1, 5, 0.5), 
      (1, -5, 0.5),  (1, -4, 0.5),  (1, -3, 0.5),  (1, -3, 0.5) , ..., (1, 5, 0.5)]

Solution for a known value of lists (i.e. known N):

I can think of a way to solve this problem for a known value of N, as shown in Code 1

Code 1:

[(a, b, th) for a in const_params_dict['a'] for b in const_params_dict['b'] for th in const_params_dict['th']]

which results in:

[(-1, -5, 0.5),
 (-1, -4, 0.5),
 (-1, -3, 0.5),
 (-1, -2, 0.5),
 (-1, -1, 0.5),
 (-1, 1, 0.5),
 (-1, 2, 0.5),
 (-1, 3, 0.5),
 (-1, 4, 0.5),
 (-1, 5, 0.5),
 (1, -5, 0.5),
 (1, -4, 0.5),
 (1, -3, 0.5),
 (1, -2, 0.5),
 (1, -1, 0.5),
 (1, 1, 0.5),
 (1, 2, 0.5),
 (1, 3, 0.5),
 (1, 4, 0.5),
 (1, 5, 0.5)]

My question:

How can I generalize this solution for an arbitrary value of N in the most elegant and efficient way?

Answer 1

Use product function of itertools likewise:

from itertools import product
list(product(*const_params_dict.values()))