Question

Possible Duplicate:
Flatten (an irregular) list of lists in Python

I have the following list —

[1,[2,3],4,[5,[6,7]]]

And I need to make it flat —

[1,2,3,4,5,6,7]

To do this, I am currently using a for loop with isinstance, with the number of loops being #nests - 1.

What woud be the simplest way to make the nested list flat? Thank you.

A similar question which deals with making a flat list out of nested lists (only) can be found here: Making a flat list out of list of lists in Python.

Answer 1

Hauled from webhelpers.misc.flatten

def flatten(iterable):
    """Recursively iterate lists and tuples.
    """
    for elm in iterable:
        if isinstance(elm, (list, tuple)):
            for relm in flatten(elm):
                yield relm
        else:
            yield elm

EDIT: The iterable test here is quite naive and can be improved by checking for the presence of __iter__ or an instance of the collections.Iterable abstract base class.

EDIT 2: @ChristopheD is absolutely correct, this is a dupe so head over to the linked question.