Any Functional Programming method of traversing a nested dictionary?

问题

I am trying to find a better way to implement this:

d = {"a": {"b": {"c": 4}}} 
l = ["a", "b", "c"]
for x in l:
    d = d[x]
print (d) # 4 

I am learning functional programming so I am just trying random example that come to my head :)

回答1:

Use reduce():

reduce(dict.__getitem__, l, d)

or better still, using operator.getitem():

from operator import getitem

reduce(getitem, l, d)

Demo:

>>> d = {"a": {"b": {"c": 4}}} 
>>> l = ["a", "b", "c"]
>>> from operator import getitem
>>> reduce(getitem, l, d)
4

Python 3 moved the reduce() function out of the built-ins and into functools.reduce().

来源：https://stackoverflow.com/questions/20324830/any-functional-programming-method-of-traversing-a-nested-dictionary