# [Solved] How to flatten a list of nested tuples in Python?

I have a list of tuples that looks like this:

``````[('a', 'b'), ('c', 'd'), (('e', 'f'), ('h', 'i'))]
``````

I want to turn it into this:

``````[('a', 'b'), ('c', 'd'), ('e', 'f'), ('h', 'i')]
``````

What is the most Pythonic way to do this?

## Solution #1:

one-line, using list comprehension:

``````l = [('a', 'b'), ('c', 'd'), (('e', 'f'), ('h', 'i'))]

result = [z for y in (x if isinstance(x[0],tuple) else [x] for x in l) for z in y]

print(result)
``````

yields:

``````[('a', 'b'), ('c', 'd'), ('e', 'f'), ('h', 'i')]
``````

this is artificially creating a list if the element is not a tuple of tuples, then flattening all does the job. To avoid creating a single element list `[x]`, `(x for _ in range(1))` can also do the job (although it appears clunky)

Limitation: doesn’t handle more than 1 level of nesting. In which case, a more complex/recursive solution must be coded (check Martijn’s answer).

## Solution #2:

Adjust the canonical un-flatten recipe to only unflatten when there are tuples in the value:

``````def flatten(l):
for el in l:
if isinstance(el, tuple) and any(isinstance(sub, tuple) for sub in el):
for sub in flatten(el):
yield sub
else:
yield el
``````

This will only unwrap tuples, and only if there are other tuples in it:

``````>>> sample = [('a', 'b'), ('c', 'd'), (('e', 'f'), ('h', 'i'))]
>>> list(flatten(sample))
[('a', 'b'), ('c', 'd'), ('e', 'f'), ('h', 'i')]
``````

## Solution #3:

A one-line solution would be using `itertools.chain`:

``````>>> l = [('a', 'b'), ('c', 'd'), (('e', 'f'), ('h', 'i'))]
>>> from itertools import chain
>>> [*chain.from_iterable(x if isinstance(x[0], tuple) else [x] for x in l)]
[('a', 'b'), ('c', 'd'), ('e', 'f'), ('h', 'i')]
``````

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