How to concatenate tuples and put it into a single item list?

Question

How can I concatenate different tuples inside a list to a single tuple inside a list in Python?

Current form:

[('1st',), ('2nd',), ('3rd',), ('4th',)]

Desired form:

[('1st', '2nd', '3rd', '4th')]

`[tuple([inner_tuple[0] for inner_tuple in list_of_tuples])]` where `list_of_tuples` is the list of tuples you posted. — aybry, Aug 24 '20 at 21:22
@wjandrea: Personally, I'd count this as a duplicate of that question; aside from using the `tuple` constructor (possibly replacing an equivalent use of the `list` constructor), every technique there applies. — ShadowRanger, Aug 24 '20 at 21:34
@KlausD.: For small inputs as in this example, that's fine, but it's a misuse of `sum`; it's a Schlemiel the Painter's algorithm, repeatedly concatenating larger and larger `tuple`s. Turns a `O(n)` operation into a `O(n²)` operation. — ShadowRanger, Aug 24 '20 at 21:35
Please [edit] your question and add your own attempt at doing this. — martineau, Aug 24 '20 at 21:39
@ShadowRanger I'd argue that the time typing more complex code (as below) will exceed the computing time ever used by it, if the number of items is not getting too large. ;) — Klaus D., Aug 24 '20 at 21:40

score 3 · Accepted Answer · edited Aug 24 '20 at 21:49

What you're trying to do is "flatten" a list of tuples. The easiest and most pythonic way is to simply use (nested) comprehension:

tups = [('1st',), ('2nd',), ('3rd',), ('4th',)]

tuple(item for tup in tups for item in tup)

result:

('1st', '2nd', '3rd', '4th')

You can wrap the resulting tuple in a list if you really want.

EDIT:

I also like Alan Cristhian's answer, which is basically transposing a column vector into a row vector:

list(zip(*tups))

score 2 · Answer 2 · answered Aug 24 '20 at 21:22

2

Seems like this will do it:

import itertools
tuples = [('1st',), ('2nd',), ('3rd',), ('4th',)]
[tuple(itertools.chain.from_iterable(tuples))]

answered Aug 24 '20 at 21:22

0x5453

score 1 · Answer 3 · answered Aug 24 '20 at 21:30

1

>>> l = [('1st',), ('2nd',), ('3rd',), ('4th',)]
>>> list(zip(*l))
[('1st', '2nd', '3rd', '4th')]

answered Aug 24 '20 at 21:30

Alan Cristhian

1

This works in this case, but if the input tuples have more than one element, it'll behave totally different: `l = [('1st', 0), ('2nd', 1), ('3rd', 2), ('4th', 3)]` -> `[('1st', '2nd', '3rd', '4th'), (0, 1, 2, 3)]` – wjandrea Aug 24 '20 at 21:42
1

@wjandrea that's how a transpose works, if you might have more columns, you can explicitly grab the first row with `[:1]` – bj0 Aug 24 '20 at 22:41

score 0 · Answer 4 · answered Aug 24 '20 at 21:22

0

Simple solution:

tups = [('1st',), ('2nd',), ('3rd',), ('4th',)]

result = ()
for t in tups:
    result += t

# [('1st', '2nd', '3rd', '4th')]
print([result])

answered Aug 24 '20 at 21:22

Aviv Yaniv

score -1 · Answer 5 · answered Aug 24 '20 at 21:32

-1

Here's another one - just for fun:

[tuple([' '.join(tup) for tup in tups])]

answered Aug 24 '20 at 21:32

Jack Fleeting

What's with the `' '.join(tup)`? That's not part of the question, and could lead to unexpected behaviour for tuples that have more than one item or don't contain all strings. – wjandrea Aug 24 '20 at 21:39
@wjandrea I don't see what your problem is. It gets the expected output to OP's input, but using a different approach. You may not like it, but downvoting it seems a little excessive. – Jack Fleeting Aug 24 '20 at 21:42

5 Answers5