在python中动态填充嵌套字典

Question

I need to populate nested dictionary in python (multiple level of dicts) dynamically inside a for loop. I can only determine the keys dynamically inside for loop. My dict looks like

dict =>
    { bucket1 => 
                {classification1 => {key1 : val1, key2 : val2}}
                {classification2 => {key1 : val1, key2 : val2}}
    } ....

I know the keys bucket1, bucket2 alone as they are fixed values. So i declare dict[bucket1] = {} and dict[bucket2] = {}. I try to populate the data inside a for loop as dict[bucket][classification1][key1] = value sample block:

for string in stringarray:
    bucket = "some string based on regex" #this can be fixed set of 2 strings
    classification = "some string based on regex"
    key = "some string based on regex"
    value = "count of the occurence of [classification1][key1]"
    dict[bucket][classification][key] = value

But I get key error. I can determine the value of classification1 inside for loop. Hence I cannot declare it intially. Traceback of the error:

    dict['bucket1']['c1']['key1'] = 4
Traceback (most recent call last):
  File "<console>", line 1, in <module>
KeyError: 'c1'

What is the efficient way to populate this kind of nested dictionary in python?

Answer 1

How about doing it with a recursive defaultdict ?

from collections import defaultdict

recursive_dict = lambda: defaultdict(recursive_dict)
my_dict = recursive_dict()

bucket = "bucket"
classification = "class"
key = "key"
value = 2
my_dict[bucket][classification][key] = value
# my_dict ==> { "bucket": { "class": { "key": 2 } } }