Nested indexing in python

Question

I have a python dict, and some (but not all) of its values are also dicts.

For example:

    d = {'a' : 1,
         'b' : {'c' : 3, 'd' : 'target_value'}
        }

What would be the best way to pass in keys to reach any target value? Something like retrieve(d, (key, nested_key, ...)) where retrieve(d, ('b','d')) would return target value.

I am parsing a file and organizing it into dictionaries which are sometimes nested. But this applies to any nested indexable data structures. — jpm
– jpm, Commented Aug 1, 2016 at 17:40
My mistake, retrieve(d, ('b', 'd')) should return target_value — jpm
– jpm, Commented Aug 1, 2016 at 17:48

Morgan Thrapp · Accepted Answer · 2016-08-01 17:52:56Z

2

The better option here is to find a way to normalize your data structure, but if you can't for some reason, you can just access each key in order.

For example:

def nested_getter(dictionary, *keys):
    val = dictionary[keys[0]]
    for key in keys[1:]:
        val = val[key]
    return val
d = {'a' : 1,
     'b' : {'c' : 3, 'd' : 'target_value'}
    }
print(nested_getter(d, 'b', 'd'))

You could also do it recursively:

def nested_getter(dictionary, *keys):
    val = dictionary[keys[0]]
    if isinstance(val, dict):
        return nested_getter(val, *keys[1:])
    else:
        return val

edited Aug 1, 2016 at 17:52

answered Aug 1, 2016 at 17:45

Morgan Thrapp

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