Is there a recursive version of the dict.get() built-in?

Question

I have a nested dictionary object and I want to be able to retrieve values of keys with an arbitrary depth. I\'m able to do this by subclassing dict:

Answer 1

@ThomasOrozco's solution is correct, but resorts to a lambda function, which is only necessary to avoid TypeError if an intermediary key does not exist. If this isn't a concern, you can use dict.get directly:

from functools import reduce

def get_from_dict(dataDict, mapList):
    """Iterate nested dictionary"""
    return reduce(dict.get, mapList, dataDict)

Here's a demo:

a = {'Alice': {'Car': {'Color': 'Blue'}}}  
path = ['Alice', 'Car', 'Color']
get_from_dict(a, path)  # 'Blue'

---

If you wish to be more explicit than using lambda while still avoiding TypeError, you can wrap in a try / except clause:

def get_from_dict(dataDict, mapList):
    """Iterate nested dictionary"""
    try:
        return reduce(dict.get, mapList, dataDict)
    except TypeError:
        return None  # or some other default value

---

Finally, if you wish to raise KeyError when a key does not exist at any level, use operator.getitem or dict.__getitem__:

from functools import reduce
from operator import getitem

def getitem_from_dict(dataDict, mapList):
    """Iterate nested dictionary"""
    return reduce(getitem, mapList, dataDict)
    # or reduce(dict.__getitem__, mapList, dataDict)

Note that [] is syntactic sugar for the __getitem__ method. So this relates precisely how you would ordinarily access a dictionary value. The operator module just provides a more readable means of accessing this method.