Multi-level defaultdict with variable depth?

I have a large list like:

[A][B1][C1]=1
[A][B1][C2]=2
[A][B2]=3
[D][E][F][G]=4

I want to build a multi-level dict like:

A
--B1
-----C1=1
-----C2=1
--B2=3
D
--E
----F
------G=4

I know that if I use recursive defaultdict I can write table[A][B1][C1]=1, table[A][B2]=2, but this works only if I hardcode those insert statement.

While parsing the list, I don't how many []'s I need beforehand to call table[key1][key2][...].

You can do it without even defining a class:

from collections import defaultdict

nested_dict = lambda: defaultdict(nested_dict)
nest = nested_dict()

nest[0][1][2][3][4][5] = 6

Your example says that at any level there can be a value, and also a dictionary of sub-elements. That is called a tree, and there are many implementations available for them. This is one:

from collections import defaultdict
class Tree(defaultdict):
    def __init__(self, value=None):
        super(Tree, self).__init__(Tree)
        self.value = value

root = Tree()
root.value = 1
root['a']['b'].value = 3
print root.value
print root['a']['b'].value
print root['c']['d']['f'].value

Outputs:

1
3
None

You could do something similar by writing the input in JSON and using json.load to read it as a structure of nested dictionaries.