Finding key in a Nested dictionary

Question

I'm trying to find a key inside a nested dictionary:

mydict = {
    ('Geography', 1): {},
    ('Languages', 2): {
        ('English', 3): {
            ('Grammar', 6): {
                ('new', 10):{},
                ('old', 11): {}
            }
        },
        ('Spanish', 4): {},
        ('French', 5):  {
            ('Grammar', 7): {}
        },
        ('Dutch', 8): {
            ('Grammar', 9): {
                ('new', 12):{}
            }
        }
    }
}

So I loop inside the dictionary to find the key ('Grammar', 9) for example:

def _loop(topic, topics_dict):
    if (topic[0], topic[1]) in topics_dict.keys():
        return topics_dict[(topic[0], topic[1])]
    else:
        for k, v in topics_dict.items():
            if v != {}:
                return _loop(topic, v)

topic = ('Grammar', 9)
trim_mydict = _loop(topic, mydict)
print(trim_mydict)

But, in fact, it returns None instead of {('new', 12):{}}

I've checked this thread (Finding a key recursively in a dictionary) but I seem to be doing the exact same thing...

Just a suggestion, did you try the other solutions on that page you linked? — NewPythonUser, May 28 '20 at 05:31
You are testing if v is NOT a dictionary before recursing. This will make the code stop immediately, since you do have nested dictionaries. Edit: sorry, i misread that :) you are just checking if it is not empty — NewPythonUser, May 28 '20 at 05:36

score 1 · Accepted Answer · answered May 28 '20 at 05:42

When you have return without a condition in the loop there it only returns the first result, even if it's None. I added a check like this:

mydict = {
    ('Geography', 1): {},
    ('Languages', 2): {
        ('English', 3): {
            ('Grammar', 6): {
                ('new', 10):{},
                ('old', 11): {}
            }
        },
        ('Spanish', 4): {},
        ('French', 5):  {
            ('Grammar', 7): {}
        },
        ('Dutch', 8): {
            ('Grammar', 9): {
                ('new', 10):{}
            }
        }
    }
}


def _loop(topic, topics_dict):
    if (topic[0], topic[1]) in topics_dict.keys():
        return topics_dict[(topic[0], topic[1])]
    else:
        for k, v in topics_dict.items():
            if v != {}:
                if (result := _loop(topic, v)) is not None:
                    return result

topic = ('Grammar', 9)
trim_mydict = _loop(topic, mydict)
print(trim_mydict)

>>> {('new', 10): {}}

Finding key in a Nested dictionary

1 Answers1