python: sorting

Question

hi im doing a loop so i could get dict of data, but since its a dict it's sorting alphabetical and not as i push it trought the loop ...

is it possible to somehow turn off alphabetical sorting?

here is how do i do that

data = {}
for item in container:
  data[item] = {}
  ...
  for key, val in item_container.iteritems():
    ...
    data[item][key] = val

whitch give me something like this

data = {
  A : { K1 : V1, K2 : V2, K3 : V3 },
  B : { K1 : V1, K2 : V2, K3 : V3 },
  C : { K1 : V1, K2 : V2, K3 : V3 }
}

and i want it to be as i was going throught the loop, e.g.

data = {
  B : {K2 : V2, K3 : V3, K1 : V1},
  A : {K1 : V1, K2 : V2, K3 : V3},
  C : {K3 : V3, K1 : V1, K2 : V2}
}

It only seems alphabetical by chance. If you add more strings to it, or other items, you'll see that it's not alphabetical at all. Dicts have no reliable order. — Thomas Wouters, Apr 13 '10 at 14:24

score 5 · Accepted Answer · answered Apr 13 '10 at 14:26

5

If you really need to use a dictionary and not a list, take a look at the new OrderedDict (Python 3.1, soon to be available in Python 2.7, too). This will preserve the order in which its items were added.

from collections import OrderedDict
data = OrderedDict()
for item in container:
  data[item] = OrderedDict()
  ...
  for key, val in item_container.iteritems():
    ...
    data[item][key] = val

answered Apr 13 '10 at 14:26

Tim Pietzcker

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I suggest you add a link to the package that provides OrderedDict for Python 2.4 through 2.6: http://pypi.python.org/pypi/ordereddict – Daniel Stutzbach Apr 13 '10 at 18:06
Oh, great - I didn't know about that. Well, you have already added the link, not much left for me to do :) – Tim Pietzcker Apr 13 '10 at 19:23

score 3 · Answer 2 · answered Apr 13 '10 at 14:22

3

You should not be relying on the sort order of data in a dict; since it is just a collection of key/value pairs, the ordering is not guaranteed by the underlying implementation and could change in a future version.

answered Apr 13 '10 at 14:22

Justin Ethier

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For more information, see: http://stackoverflow.com/questions/613183/python-sort-a-dictionary-by-value – Justin Ethier Apr 13 '10 at 14:23

score 0 · Answer 3 · answered Apr 13 '10 at 15:27

You can use a list of lists, instead of a dict of dicts. Each element would be a tuple of (key,value). Of course, this means you won't be able to retrieve elements by keys, but it will preserve order. I'm not sure if its a good idea, because I don't really know what you're trying to do, but its an option.

python: sorting

3 Answers3