How can I get my function to return more than 1 result (with for-loops and dictionaries) in Python?

Question

I am trying to find a way to return more than one result for my dictionary in Python:

def transitive_property(d1, d2):
    '''
    Return a new dictionary in which the keys are from d1 and the values are from d2. 
    A key-value pair should be included only if the value associated with a key in d1
    is a key in d2.  

    >>> transitive_property({'one':1, 'two':2}, {1:1.0})
    {'one':1.0}
    >>> transitive_property({'one':1, 'two':2}, {3:3.0})
    {}
    >>> transitive_property({'one':1, 'two':2, 'three':3}, {1:1.0, 3:3.0})
    {'one':1.0}
    {'three': 3.0}
    '''
    for key, val in d1.items():
        if val in d2:
            return {key:d2[val]}
        else:
            return {}

I've come up with a bunch of different things but they would never pass a few test cases such as the third one (with {'three':3}). This what results when I test using the third case in the doc string:

{'one':1.0}

So since it doesn't return {'three':3.0}, I feel that it only returns a single occurrence within the dictionary, so maybe it's a matter of returning a new dictionary so it could iterate over all of the cases. What would you say on this approach? I'm quite new so I hope the code below makes some sense despite the syntax errors. I really did try.

empty = {}
for key, val in d1.items():
    if val in d2:
        return empty += key, d2[val]

return empty

Answer 1

If return is used to , then the function is terminated for that particular call . So if you want to return more than one value it is impossible. You can use arrays instead .You can store values in array and the return thhe array.

Answer 2

Your idea almost works but (i) you are returning the value immediately, which exits the function at that point, and (ii) you can't add properties to a dictionary using += . Instead you need to set its properties using dictionary[key] = value .

result = {}
for key, val in d1.items():
    if val in d2:
        result[key] = d2[val]

return result

This can also be written more succinctly as a dictionary comprehension:

def transitive_property(d1, d2):
    return {key: d2[val] for key, val in d1.items() if val in d2}

You can also have the function return a list of dictionaries with a single key-value pair in each, though I'm not sure why you would want that:

def transitive_property(d1, d2):
    return [{key: d2[val]} for key, val in d1.items() if val in d2]