How to preserve the ordering of keys when declaring a dictionary

Question

My goal is to preserve the ordering of keys in a dictionary declaration. I am using collections.OrderedDict but when I run:

>>> modelConfigBase = OrderedDict({'FC':'*','EC':'*','MP':'*','LP':'*','ST':'*','SC':'*'})

The order changes:

>>> modelConfigBase
OrderedDict([('EC', '*'), ('ST', '*'), ('FC', '*'), ('MP', '*'), ('LP', '*'), ('SC', '*')])

What am I doing wrong?

Once the dictionary is created, there is no key ordereing. In your case, the dictionary which is created already is passed to `OrderedDict` — thefourtheye, Jan 15 '16 at 18:27
The repr value that prints in the interactive interpreter shows you how to create the object. In this case, use a list of tuples. — Air, Jan 15 '16 at 18:35
Duplicate of [Converting Dict() to OrderedDict()](http://stackoverflow.com/questions/15711755/converting-dict-to-ordereddict) — SirParselot, Jan 15 '16 at 18:36

mgilson · Accepted Answer · 2016-01-15T18:36:09.087

The dictionary that you are passing to OrderedDict is unordered. You need to pass an ordered iterable of items . . .

e.g.

modelConfigBase = OrderedDict([
    ('FC', '*'),
    ('EC', '*'),
    ('MP', '*'),
    ('LP', '*'),
    ('ST', '*'),
    ('SC', '*')])

Note that, in this case (since all the values are the same), it looks like you could get away with the simpler:

modelConfigBase = OrderedDict.fromkeys(['FC', 'EC', 'MP', 'LP', 'ST', 'SC'], '*')

score 0 · Answer 2 · answered Jan 15 '16 at 18:35

0

Based on thefourtheye response the solution is as follows:

modelConfigBase = OrderedDict([('EC', '*'), ('ST', '*'), ('FC', '*'), ('MP', '*'), ('LP', '*'), ('SC', '*')])

answered Jan 15 '16 at 18:35

pemfir

2 Answers2