Converting dict to OrderedDict

问题:

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.

回答1:

You are creating a dictionary first, then passing that dictionary to an OrderedDict. 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.

回答2:

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)

回答3:

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)