Randomly assign a pair to each item in a list without repetitions

Question

So I have a list and I would like to "assign" the values to a different random value.

For eg.

list = ["dog", "cat", "rat", "bird", "monkey"]

I would like an output like

{"dog": "bird", "cat": "monkey", "rat": "dog", "bird": "rat", "monkey": "cat"}

What I would like is:

• A value can't be assigned to itself e.g not {"cat": "cat"}
• A value can only be assigned once e.g not {"cat": "dog", "rat": "dog"}
• Values can't be assigned to each other e.g not {"cat": "dog", "dog", "cat"}

I tried this code:

def shuffle_recur(_list):
    final = {}
    not_done = copy.deepcopy(_list)
    for value in _list:
        without_list = not_done.copy()
        if value in without_list :
            without_list.remove(value)
        if value in final.values():
            for final_key, final_value in final.items():
                if final_value == value:
                    print(final_value, '    ', final_key)
                    if final_key in without_list :
                        without_list.remove(final_key)
        if len(without_list) < 1:
            print('less')
            return shuffle_recur(_list)
        target = random.choice(without_list)
        not_done.remove(target)
        final[value] = target
        print('{} >> {}'.format(value, target))
    return final

But it is very messy and I don't think it the the best way. What would be a better way to do this?

Answer 1

You may just build a random-ordered list of your items, then pair them as key-value

From one hand you'll take the list, in the other hand the same list rotated from on item values[1:] + [values[0]], and you zip both to pair 2-by-2 pairs, and build a dict from these pairs

values = ["dog", "cat", "rat", "bird", "monkey"]
shuffle(values)
result = dict(zip(values, values[1:] + [values[0]]))

Example

• shuffling gives ['bird', 'dog', 'rat', 'monkey', 'cat']

• rotating gives ['dog', 'rat', 'monkey', 'cat', 'bird']

• zipping gives [('bird', 'dog'), ('dog', 'rat'), ('rat', 'monkey'), ('monkey', 'cat'), ('cat', 'bird')]

• then each pair becomes a mapping

print(values)  # ['bird', 'dog', 'rat', 'monkey', 'cat']
print(result)  # {'bird': 'dog', 'dog': 'rat', 'rat': 'monkey', 'monkey': 'cat', 'cat': 'bird'}

---

If you don't the mapping to be following each other, just shuffle a second time

mappings = list(zip(values, values[1:] + [values[0]]))
shuffle(mappings)
result = dict(mappings)