Creating a nested dictionary from a flattened dictionary

Question

I have a flattened dictionary which I want to make into a nested one, of the form

flat = {\'X_a_one\': 10,
        \'X_a_two\': 20, 
        \'X_b_one\': 10,         


        

Answer 1

output = {}

for k, v in source.items():
    # always start at the root.
    current = output

    # This is the part you're struggling with.
    pieces = k.split('_')

    # iterate from the beginning until the second to last place
    for piece in pieces[:-1]:
       if not piece in current:
          # if a dict doesn't exist at an index, then create one
          current[piece] = {}

       # as you walk into the structure, update your current location
       current = current[piece]

    # The reason you're using the second to last is because the last place
    # represents the place you're actually storing the item
    current[pieces[-1]] = v