Reorganize Dictionary

Question

I have a .csv file that I've read into python using csv.dictwriter that looks something like this:

[
    {'id':'1', 'date':'12312004','var1':'234', 'var2':'456'},
    {'id':'1', 'date':'12312005','var1':'200', 'var2':'466'},
    {'id':'1', 'date':'12312006','var1':'760', 'var2':'656'},
    {'id':'1', 'date':'12312007','var1':'215', 'var2':'256'},
    {'id':'2', 'date':'5312006','var1':'234', 'var2':'456'},
    {'id':'2', 'date':'5312007','var1':'200', 'var2':'466'},
    {'id':'2', 'date':'5312008','var1':'760', 'var2':'656'},
    {'id':'2', 'date':'5312009','var1':'215', 'var2':'256'},
]

I'd like to reorganize it to:

{'1': {
    '12312004': {'var1': '234', 'var2': '456'},
    '12312005': {'var1': '200', 'var2': '466'},
    '12312006': {'var1': '760', 'var2': '656'},
    '12312007': {'var1': '215', 'var2': '256'}},
 '2': {
     '5312006': {'var1': '234', 'var2': '456'},
     '5312007': {'var1': '200', 'var2': '466'},
     '5312008': {'var1': '760', 'var2': '656'},
     '5312009': {'var1': '215', 'var2': '256'}}
}

Neither input nor desired output are valid Python. Can you please use ASCII quotes (`'` or `"`) and make it clear what type of object your input is (is it a list perhaps?). — Martijn Pieters, Jul 30 '15 at 17:58
Sorry. I wrote this in a text editor and it didn't past well. Thanks for fixing it. — Chad Larson, Jul 30 '15 at 18:13

score 2 · Accepted Answer · answered Jul 30 '15 at 18:01

Provided your input is a list, you can do this:

output = {}
for entry in input_list:
    entry = entry.copy()  # so we can mangle it
    id = entry.pop('id')
    date = entry.pop('date')
    output.setdefault(id, {})[date] = entry

The dict.setdefault() call returns the value for the key id, but if there is no such key, the second argument will be added to the output dictionary for that key and returned instead.

Demo:

>>> input_list = [
...     {'id':'1', 'date':'12312004','var1':'234', 'var2':'456'},
...     {'id':'1', 'date':'12312005','var1':'200', 'var2':'466'},
...     {'id':'1', 'date':'12312006','var1':'760', 'var2':'656'},
...     {'id':'1', 'date':'12312007','var1':'215', 'var2':'256'},
...     {'id':'2', 'date':'5312006','var1':'234', 'var2':'456'},
...     {'id':'2', 'date':'5312007','var1':'200', 'var2':'466'},
...     {'id':'2', 'date':'5312008','var1':'760', 'var2':'656'},
...     {'id':'2', 'date':'5312009','var1':'215', 'var2':'256'},
... ]
>>> output = {}
>>> for entry in input_list:
...     entry = entry.copy()  # so we can alter it
...     id = entry.pop('id')
...     date = entry.pop('date')
...     output.setdefault(id, {})[date] = entry
... 
>>> from pprint import pprint
>>> pprint(output)
{'1': {'12312004': {'var1': '234', 'var2': '456'},
       '12312005': {'var1': '200', 'var2': '466'},
       '12312006': {'var1': '760', 'var2': '656'},
       '12312007': {'var1': '215', 'var2': '256'}},
 '2': {'5312006': {'var1': '234', 'var2': '456'},
       '5312007': {'var1': '200', 'var2': '466'},
       '5312008': {'var1': '760', 'var2': '656'},
       '5312009': {'var1': '215', 'var2': '256'}}}

Reorganize Dictionary

1 Answers1

Linked