How to access nested dictionary items via a list of keys with Python?

Sometimes, we want to access nested dictionary items via a list of keys with Python.

In this article, we’ll look at how to access nested dictionary items via a list of keys with Python.

How to access nested dictionary items via a list of keys with Python?

To access nested dictionary items via a list of keys with Python, we can use the reduce function with the operator.getitem method to get the dictionary item with the array of keys forming the path to the dictionary item.

For instance, we write:

from functools import reduce
import operator


def getFromDict(data_dict, map_list):
    return reduce(operator.getitem, map_list, data_dict)


def setInDict(data_dict, map_list, value):
    getFromDict(data_dict, map_list[:-1])[map_list[-1]] = value


data_dict = {
    "a": {
        "r": 1,
        "s": 2,
        "t": 3
    },
    "b": {
        "u": 1,
        "v": {
            "x": 1,
            "y": 2,
            "z": 3
        },
        "w": 3
    }
}

map_list = ["a", "r"]

setInDict(data_dict, map_list, 100)
print(data_dict)

We have the getFromDict function that calls reduce with the mapList and dataDict to get the item from data_dict with the path of the dictionary formed by map_list list.

Then we have the setInDict function that use getFromDict with the data_dict and map_list to get dictionary item from data_dict with the path to the item formed by map_list.

Then we set the value of the retrieved dictionary item to value.

Next, we call setInDict with data_dict, map_list and 100 to set data_list['a']['r'] to 100.

Therefore, data_dict is now:

{'a': {'r': 100, 's': 2, 't': 3}, 'b': {'u': 1, 'v': {'x': 1, 'y': 2, 'z': 3}, 'w': 3}}

How to access nested dictionary items via a list of keys with Python?

Conclusion