Differences between revisions 2 and 3
 ⇤ ← Revision 2 as of 2003-11-21 19:32:38 → Size: 579 Editor: dsl254-010-130 Comment: Question: This a good way? ← Revision 3 as of 2003-11-21 19:45:06 → ⇥ Size: 847 Editor: ip503dabc3 Comment: add name of pattern, reformat code and rename some variables Deletions are marked like this. Additions are marked like this. Line 11: Line 11: a = { "key1":5, "key2":8, "key3":2 }b = { "key1":7, "key2":4, "key3":9 }c = { "key1":6, "key2":1, "key3":1 }l = [ a,b,c ] # how do you sort this list? a = {"key1": 5 , "key2": 8, "key3": 2}b = {"key1": 7 , "key2": 4, "key3": 9}c = {"key1": 6 , "key2": 1, "key3": 1}undecorated = [a, b, c] # how do you sort this list? Line 17: Line 17: There are many ways to do this; Here's one way I've been doing it: There are many ways to do this. Here's the fastest way to do it, as it avoids using a custom comparison function, instead using builtin comparisons. This is the ''decorate-sort-undecorate'' (DSU) pattern, or the ''Schwartzian transform'' if you're coming from Perl. Line 21: Line 21: sort_key = "key2"l = [(d[sort_key],d) for d in l]l.sort()l = [d for (k,d) in l] sort_on = "key2"decorated = [(dict_[sort_on], dict_) for dict_ in undecorated]decorated.sort()sorted = [dict_ for (key, dict_) in l]

# Sorting Lists of Dictionaries

Frequently you want to sort a list of dictionaries, based on some particular key.

For example:

```   1 a = {"key1": 5 , "key2": 8, "key3": 2}
2 b = {"key1": 7 , "key2": 4, "key3": 9}
3 c = {"key1": 6 , "key2": 1, "key3": 1}
4 undecorated = [a, b, c] # how do you sort this list?
```

There are many ways to do this. Here's the fastest way to do it, as it avoids using a custom comparison function, instead using builtin comparisons. This is the decorate-sort-undecorate (DSU) pattern, or the Schwartzian transform if you're coming from Perl.

```   1 sort_on = "key2"
2 decorated = [(dict_[sort_on], dict_) for dict_ in undecorated]
3 decorated.sort()
4 sorted = [dict_ for (key, dict_) in l]
```

## Questions

This a good way? -- LionKimbro

SortingListsOfDictionaries (last edited 2010-03-30 19:08:00 by wl-ol-s246-130)

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