[Tutor] Sorting Dictionary of Dictionary by certain Value

[John Fouhy]

2008/9/24 Joe Python <jopython at gmail.com>:
> Hi Pythonistas,
>
> I have a large dictionary of dictionary (50,000+ keys) which has a structure
> as follows:
[snip]
> I want to sort the dictionary by 'income'
> Is there an efficient way to do the same.

Note that you cannot sort a dictionary.  The best you can do is build
a list containing the dictionary keys in the appropriate order and use
the dictionary in combination with that list.

You could try this:

1. Build a dictionary mapping income to list of families.
2. Sort keys to this dictionary.
3. Iterate through this sorted list, emitting family names.

e.g.

from collections import defaultdict
familiesByIncome = defaultdict(list)
for family in DoD:
  familiesByIncome[DoD[family]['income']].append(family)

incomes = familiesByIncome.keys()
incomes.sort()     # sorts from lowest to highest

familiesSorted = []
for inc in incomes:
  familiesSorted.extend(familiesByIncome[inc])

##

HTH!

-- 
John.