list of duplicate dictionaries copy single entry to another list

Question

Hello,

newbie question again.

Let's say i have a list of nested dictionaries.

a = [{"value1": 1234, "value2": 23423423421, "value3": norway, "value4": charlie},
     {"value1": 1398, "value2": 23423412221, "value3": england, "value4": alpha},
     {"value1": 1234, "value2": 23234231221, "value3": norway, "value4": charlie},
     {"value1": 1398, "value2": 23423213121, "value3": england, "value4": alpha}]

What i want is to move a singularis entry of each duplicate where value1, value3 and value4 matches. The result should be looking like this:

b = [{"value1": 1398, "value2": 23423412221, "value3": england, "value4": alpha},
     {"value1": 1234, "value2": 23234231221, "value3": norway, "value4": charlie}]

The orginal list, a, should remain in it's orginal state.

Answer 1

There was a similar question on this recently. Try this entry.

In fact, you asked that question: "Let's say there exists multiple entries where value3 and value4 are identical to other nested dictionaries. How can i quick and easy find and remove those duplicate dictionaries."

It sounds like the same thing, right?

Edit: liberally stealing Alex's code, it looks something like this:

import itertools
import pprint
import operator

alpha, charlie, norway, england = range(4)

a = [{"value1": 1234, "value2": 23423423421, "value3": norway, "value4": charlie},
     {"value1": 1398, "value2": 23423412221, "value3": england, "value4": alpha}, 
     {"value1": 1234, "value2": 23234231221, "value3": norway, "value4": charlie}, 
     {"value1": 1398, "value2": 23423213121, "value3": england, "value4": alpha}]


getvals = operator.itemgetter('value1', 'value3', 'value4')

a.sort(key=getvals)

b = [g.next() for _, g in itertools.groupby(a, getvals)]
pprint.pprint(b)

And the result is:

[{'value1': 1234, 'value2': 23423423421L, 'value3': 2, 'value4': 1},
 {'value1': 1398, 'value2': 23423412221L, 'value3': 3, 'value4': 0}]