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pythonlistgrouping

Group list by values

Let's say I have a list like this:

mylist = [["A",0], ["B",1], ["C",0], ["D",2], ["E",2]]

How can I most elegantly group this to get this list output in Python:

[["A", "C"], ["B"], ["D", "E"]]

So the values are grouped by the secound value but the order is preserved...

Solution 
  • values = set(map(lambda x:x[1], mylist))
newlist = [[y[0] for y in mylist if y[1]==x] for x in values]