Combinations from dictionary with list values using Python

Question

I have the following incoming value:

variants = {
  \"debug\" : [\"on\", \"off\"],
  \"locale\" : [\"de_DE\", \"en_US\", \"fr_FR\"],
  ...
}

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Answer 1

I assume you want the cartesian product of all the keys? So if you had another entry, "foo", with values [1, 2, 3], then you'd have 18 total entries?

First, put the values in a list, where each entry is one of the possible variants in that spot. In your case, we want:

[[{'debug': 'on'}, {'debug': 'off'}], [{'locale': 'de_DE'}, {'locale': 'en_US'}, {'locale': 'fr_FR'}]]

To do that:

>>> stuff = []
>>> for k,v in variants.items():
    blah = []
    for i in v:
        blah.append({k:i})
    stuff.append(blah)


>>> stuff
[[{'debug': 'on'}, {'debug': 'off'}], [{'locale': 'de_DE'}, {'locale': 'en_US'}, {'locale': 'fr_FR'}]]

Next we can use a Cartesian product function to expand it...

>>> def cartesian_product(lists, previous_elements = []):
if len(lists) == 1:
    for elem in lists[0]:
        yield previous_elements + [elem, ]
else:
    for elem in lists[0]:
        for x in cartesian_product(lists[1:], previous_elements + [elem, ]):
            yield x


>>> list(cartesian_product(stuff))
[[{'debug': 'on'}, {'locale': 'de_DE'}], [{'debug': 'on'}, {'locale': 'en_US'}], [{'debug': 'on'}, {'locale': 'fr_FR'}], [{'debug': 'off'}, {'locale': 'de_DE'}], [{'debug': 'off'}, {'locale': 'en_US'}], [{'debug': 'off'}, {'locale': 'fr_FR'}]]

Note that this doesn't copy the dicts, so all the {'debug': 'on'} dicts are the same.