Unpacking List of Tuples of List(s)

Question

I have a list of tuples where one of the elements in the tuple is a list.

example = [([0, 1, 2], 3, 4), ([5, 6, 7], 8, 9)]

I'd like to end up with just a list of tuples

output = [(0, 1, 2, 3, 4), (5, 6, 7, 8, 9)]

This question seems to address the issue with tuples but I am concerned as my use case has many more elements in the inner list and

[(a, b, c, d, e) for [a, b, c], d, e in example]

seems tedious. Is there a better way to write this?

Do all your tuples match the `([a, b, c], d, e)` pattern exactly ? — ereOn, May 20 '15 at 16:33
Yes. The actual list i have has 100 elements but the 100 is uniform and it will always have 2 elements on the outside. — o-90, May 20 '15 at 16:35
If all the tuples in the list match the pattern of ([a, b, c], d, e), then your code is pythonic and doesn't seem tedious. — user1823, May 20 '15 at 16:35
Could the position of the list in the tuple change or is it fixed ? — ereOn, May 20 '15 at 16:50

score 5 · Accepted Answer · answered May 20 '15 at 16:47

Tuples can be concatenated with + like lists. So, you can do:

>>> example = [([0, 1, 2], 3, 4), ([5, 6, 7], 8, 9)]
>>> [tuple(x[0]) + x[1:] for x in example]
[(0, 1, 2, 3, 4), (5, 6, 7, 8, 9)]

Note that this works in both Python 2.x and 3.x.

score 4 · Answer 2 · answered May 20 '15 at 16:38

4

In Python3 you could also do:

[tuple(i+j) for i, *j in x]

if you don't want to spell out each part of your input

answered May 20 '15 at 16:38

junnytony

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I love it ! Care to explain what exactly happens for the poor fellas like me still stuck with Python 2.x ? – ereOn May 20 '15 at 16:46
`SyntaxError: invalid syntax` on the `*j` happens for Python2.x. – wflynny May 20 '15 at 16:50

ereOn · Answer 3 · 2015-05-20T16:51:13.167

If writing a function is an option:

from itertools import chain

def to_iterable(x):
    try:
        return iter(x)
    except TypeError:
        return x,

example = [([0, 1, 2], 3, 4), ([5, 6, 7], 8, 9)]
output = [tuple(chain(*map(to_iterable, item))) for item in example]

Which gives:

print(output)
[(0, 1, 2, 3, 4), (5, 6, 7, 8, 9)]

It's way more verbose than the other solutions, but has the neat advantage of working no matter the position or number of lists in the inner tuples. Depending on your requirements this might be overkill or a good solution.

Unpacking List of Tuples of List(s)

3 Answers3