Converting dict to OrderedDict

Question

I am having some trouble using the collections OrderedDict class  I am using Python 2 7 on Raspbian  the Debian distro for Raspberry Pi  I am trying to print two dictionaries in order for comparison  side-by-side  for a text-adventure  The order is essential to compare accurately  No matter what I try the dictionaries print in their usual unordered way   Here s what I get when I do it on my RPi   import collections  ship     NAME    Albatross             HP  50            BLASTERS  13            THRUSTERS  18            PRICE  250   ship   collections OrderedDict ship   print ship   OrderedDict    PRICE   250     HP   50     NAME    Albatross      BLASTERS   13     THRUSTERS   18      Obviously there is something not right because it is printing the function call and putting the keys and value groups into a nested list     This is what I got by running something similar on my PC   import collections  Joe     Age   28   Race    Latino    Job    Nurse   Bob     Age   25   Race    White    Job    Mechanic    Random    stuff     Just for clarity  Joe   collections OrderedDict Joe  Bob   collections OrderedDict Bob   print Joe   OrderedDict    Age   28     Race    Latino      Job    Nurse     print Bob   OrderedDict    Age   25     Race    White      Job    Mechanic      Random    stuff       This time  it is in order  but it shouldn t be printing the other things though right   The putting it into list and showing function call    Where am I making my error  It shouldn t be anything to do with the pi version of Python because it is just the Linux version

User · Answer

Most of the time we go for OrderedDict when we required a custom order not a generic one like ASC etc.

Here is the proposed solution:

import collections
ship = {"NAME": "Albatross",
         "HP":50,
         "BLASTERS":13,
         "THRUSTERS":18,
         "PRICE":250}

ship = collections.OrderedDict(ship)

print ship


new_dict = collections.OrderedDict()
new_dict["NAME"]=ship["NAME"]
new_dict["HP"]=ship["HP"]
new_dict["BLASTERS"]=ship["BLASTERS"]
new_dict["THRUSTERS"]=ship["THRUSTERS"]
new_dict["PRICE"]=ship["PRICE"]


print new_dict

This will be output:

OrderedDict([('PRICE', 250), ('HP', 50), ('NAME', 'Albatross'), ('BLASTERS', 13), ('THRUSTERS', 18)])
OrderedDict([('NAME', 'Albatross'), ('HP', 50), ('BLASTERS', 13), ('THRUSTERS', 18), ('PRICE', 250)])

Note: The new sorted dictionaries maintain their sort order when entries are deleted. But when new keys are added, the keys are appended to the end and the sort is not maintained.(official doc)

User · Answer

You can create the ordered dict from old dict in one line  from collections import OrderedDict ordered dict   OrderedDict sorted ship items     The default sorting key is by dictionary key  so the new ordered dict is sorted by old dict s keys

User · Answer

You are creating a dictionary first  then passing that dictionary to an OrderedDict  For Python versions  lt  3 6      by the time you do that  the ordering is no longer going to be correct  dict is inherently not ordered   Pass in a sequence of tuples instead   ship      NAME    Albatross              HP   50             BLASTERS   13             THRUSTERS   18             PRICE   250   ship   collections OrderedDict ship    What you see when you print the OrderedDict is it s representation  and it is entirely correct  OrderedDict    PRICE   250     HP   50     NAME    Albatross      BLASTERS   13     THRUSTERS   18    just shows you  in a reproducable representation  what the contents are of the OrderedDict          In the CPython 3 6 implementation  the dict type was updated to use a more memory efficient internal structure that has the happy side effect of preserving insertion order  and by extension the code shown in the question works without issues  As of Python 3 7  the Python language specification has been updated to require that all Python implementations must follow this behaviour  See this other answer of mine for details and also why you d still may want to use an OrderedDict   for certain cases

User · Answer

Use dict items    it can be as simple as following   ship   collections OrderedDict ship items

User · Answer

If you can t edit this part of code where your dict was defined you can still order it at any point in any way you want  like this   from collections import OrderedDict  order of keys     key1    key2    key3    key4    key5   list of tuples     key  your dict key   for key in order of keys  your dict   OrderedDict list of tuples

[python] Converting dict to OrderedDict

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