Python: best way to find out from which set the results of `symmetric_difference` are from?

Question

What is the best practice for finding out from which set the results of symmetric_difference are from?

intersect = s1.symmetric_difference(s2)

The result should look like

{'34':'s1', '66':'s2'}

Where '34','66' are the unique items.

score 3 · Accepted Answer · answered Aug 07 '13 at 11:42

3

To do this most cleanly, the following should work:

intersect = s1.symmetric_difference(s2)
result = dict([(i, ("s1" if i in s1 else "s2")) for i in intersect])

answered Aug 07 '13 at 11:42

qaphla

`dict([(x,y) for ...])` can be better written as `dict((x,y) for ...)`. The additional brackets create an unnecessary list that is then immediately converted to a dictionary, so not using them will both look cleaner and run faster. – Matt Bryant Aug 09 '13 at 05:56

score 1 · Answer 2 · answered Aug 07 '13 at 11:42

1

{x : 's1' for x in intersect if x in s1} + {x : 's2' for x in intersect if x in s2}

or

{x : ('s1' if x in s1 else 's2') for x in intersect}

answered Aug 07 '13 at 11:42

YXD

2 Answers2