Get a value from multidimensional, with variable number of dimensions, dictionary in python

Question

I have a multidimensional dictionary. List of dimensions is given as a variable. How do I use all the dimensions in that list and access the value stored at the end.

def get_value(dict, dimensions):
    """
    dict is the multidimensional dict
    dimensions is a list of strings which specify all the dimensions
    """

How do I write the below command in a pythonic way

    dict[dimensions[0]][dimensions[1]][dimensions[2]]......[dimensions[len(dimensions)-1]]

First one warning - using Python reserved words for variable names is dangerous, in your case you use `dict`. I usually use `dct` for this purpose. — Jan Vlcinsky, Apr 25 '14 at 18:10

score 2 · Accepted Answer · answered Apr 25 '14 at 18:14

not too difficult, suppose you wrote this in a slightly different way:

dict = dict[dimensions[0]]
dict = dict[dimensions[1]]
dict = dict[dimensions[2]]
......
dict = dict[dimensions[len(dimensions)-1]]

we see a pattern. Another thing to notice is that we're just iterating through dimensions, we can do this as:

for d in dimensions:
    dict = dict[d]

so, in fact, we can do:

def get_value(mapping, keys):
    for key in keys:
        mapping = mapping[key]
    return mapping

Interestingly, python has a shortcut for this pattern, repeatedly applying an operation to an initial element, one for each element of another sequence, reduce()

def get_value(mapping, keys):
    return reduce(dict.get, keys, mapping)

Thanks for the answer and steps one might/should take to arrive at that. — user462455, Apr 25 '14 at 18:24

Get a value from multidimensional, with variable number of dimensions, dictionary in python

1 Answers1