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I want to zip the following list of lists:

>>> zip([[1,2], [3,4], [5,6]])
[[1,3,5], [2,4,6]]

This could be achieved with the current zip implementation only if the list is split into individual components:

>>> zip([1,2], [3,4], [5,6])
   (1, 3, 5), (2, 4, 6)]

Can't figure out how to split the list and pass the individual elements to zip. A functional solution is preferred.

Vijay Mathew
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1 Answers1

187

Try this:

>>> zip(*[[1,2], [3,4], [5,6]])
[(1, 3, 5), (2, 4, 6)]

See Unpacking Argument Lists:

The reverse situation occurs when the arguments are already in a list or tuple but need to be unpacked for a function call requiring separate positional arguments. For instance, the built-in range() function expects separate start and stop arguments. If they are not available separately, write the function call with the *-operator to unpack the arguments out of a list or tuple:

>>> range(3, 6)             # normal call with separate arguments
[3, 4, 5]
>>> args = [3, 6]
>>> range(*args)            # call with arguments unpacked from a list
[3, 4, 5]
Mark Byers
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    See http://docs.python.org/tutorial/controlflow.html#unpacking-argument-lists for how this works. – ameer Nov 06 '10 at 07:04
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    I'd like to see an alternative in case you have a list with a million entries. It might not be a good idea to unpack a million items in a function call... – Blixt Jul 29 '13 at 23:49