Python - collect output of recursive function

Question

I have written a function designed to flatten a json. The function works recursively - if a key, value pair's value is not a json, the key,value pair is returned, otherwise, the function is called again on the value:

def flatten_json(j):
    for k, v in j.items():
        if isinstance(v, dict):
            flatten_json(v)
        else:
            yield (k,v)

flat_json = {x[0]: x[1] for x in flatten_json(j)}

The idea being that whenever the function yields a tuple, it is collected into the flat_json dict. As it stands, nested outputs are ignored - only the top level key, value pairs appear in flat_json.

do the nested keys need to be prefixed with their "parent" keys somehow? or just appear as-as in the flat_json as top level keys with the same name? — Adam.Er8
– Adam.Er8, Commented Nov 13, 2019 at 14:06
@Adam.Er8 No, they don't, so, for example: {'foo': 'bar, 'foo1': 'bar1', 'nest1': {'foo2': 'bar2'}} should return {'foo': 'bar, 'foo1': 'bar1', 'foo2': 'bar2'} — alex_halford
– alex_halford, Commented Nov 13, 2019 at 14:19

Adam.Er8 · Accepted Answer · 2019-11-13 14:38:33Z

5

This is exactly what yield from is for :), to yield elements one by one from calling a generator from within a generator (whether that is a recursive call or not).

try:

def flatten_json(j):
    for k, v in j.items():
        if isinstance(v, dict):
            yield from flatten_json(v)
        else:
            yield (k,v)


j = {'foo': 'bar', 'foo1': 'bar1', 'nest1': {'foo2': 'bar2'}}
flat_json = {x[0]: x[1] for x in flatten_json(j)}
print(flat_json)

Output:

{'foo': 'bar', 'foo1': 'bar1', 'foo2': 'bar2'}

running example here: https://ideone.com/Z5aO9V

answered Nov 13, 2019 at 14:38

Adam.Er8

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Comments

Alex Hall · Accepted Answer · 2019-11-13 14:01:36Z

0

Yield it like the normal data:

yield (k, flatten_json(v))

answered Nov 13, 2019 at 14:01

Alex Hall

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