How to reduce the sets in dict values using comprehension?

Question

I have

x = {'a':set([1]) , 'b':set([2]), 'c':set([3]) }

It is guaranteed that there is only one element in the set. I need to convert this to

{'a': 1, 'c': 3, 'b': 2}

Following works:

x1 = {k:x[k].pop() for k in x.keys()}  OR
x1 = {k:next(iter(x[k])) for k in x.keys()}

but I am not liking it as pop() here is modifying the original collection. I need help on following.

• How can I use unpacking as mentioned here within comprehension.
• Is there any way, I can use functools.reduce for this.
• What can be a better or Pythonic way of doing this overall?

Answer 1

如果你想通过拆包来做到这一点，那就是

{k: item for k, [item] in x.iteritems()}

Answer 2

In my opinion, the most readable option would be to use next and iter . Unpacking might also not be of much use since it is more of an assignment operation. (See user2357112's answer)

How about simply:

>>> {k: next(iter(v)) for k, v in x.items()}
{'a': 1, 'c': 3, 'b': 2}