Recursive function return None

Question

I have a function that runs over an API output and should return the path to specific key. Here is the function:

def find_path(obj, val, path=''):
    if isinstance(obj, dict):
        for k, v in obj.items():
            if k == val:
                return f'{path}[{k!r}]'
            return find_path(v, val, path + f'[{k!r}]')
    elif isinstance(obj, list):
        for i, v in enumerate(obj):
            if v == val:
                return f'{path}[{i!r}]'
            return find_path(v, val, path + f'[{i!r}]') 

API output Example:

ex = {'Resources': [{'uschemas': {'emailSelfUpdateAllowed': True,
                                  'emailVerificationDays': 30,
                                  'approvers': {'manager': False,
                                                'secondLevelManager': False,
                                                'owner': False,
                                                'workGroup': 'workgroup'}}}]}

When I run the function I get None :

bla = find_path(ex, 'approvers')
print(bla)
>>> None

I expect to get:

['Resources'][0]['uschemas']['approvers']

I can only get the expected output when I am using the function with print instead of return .

Can someone help me to understand why? and how can I make it work with returns and not prints because I need to use its output.

Thank you.

Answer 1

You need to return value after the for loop is done, this is the value returns from the recursion, if you don't have anything it will return None

def find_path(obj, val, path=''):
    p = []
    if isinstance(obj, dict):
        for k, v in obj.items():
            if k == val:
                return f'{path}[{k!r}]'
            p = find_path(v, val, path + f'[{k!r}]')
        return p
    elif isinstance(obj, list):
        for i, v in enumerate(obj):
            if v == val:
                return f'{path}[{i!r}]'
            p = find_path(v, val, path + f'[{i!r}]')
        return p

bla = find_path(ex, 'approvers')
print(bla) # ['Resources'][0]['uschemas']['approvers']