README.md

Flatten any multi-level nested iterable, and return a new iterable.

Testing:

after installing the requirements, just run py.test tests.py, it will generate several test cases automatically

Example:

In [1]: from flatten import Flatten

In [2]: a = [[2,3,[4,5],6],7,8,[[2,3],[5,6]]]

In [3]: Flatten(a).to_list()
Out[3]: [2, 3, 4, 5, 6, 7, 8, 2, 3, 5, 6]

flatten.py

# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals

from collections import Iterable


class Flatten(object):
    """
    Iterable to flatten multi-level nested iterables
    """

    def __init__(self, iterator):
        self.iterator = iter(iterator)

    def __iter__(self):
        for value in self.iterator:
            if isinstance(value, Iterable):
                # Recurse if it's nested, could be rewritten to keep a heap
                # and thus remove the recursion
                yield from Flatten(value)
            else:
                yield value

    def to_list(self):
        """Just to avoid devs having to do list(Flatten(iterable))"""
        return list(self)

requirements.txt

pytest
hypothesis

tests.py

# -*- coding: utf-8 -*-
from __future__ import absolute_import, unicode_literals

from pprint import pprint as pp
from hypothesis import given, example
from hypothesis.strategies import lists, integers, recursive

from flatten import Flatten


nested_lists = recursive(lists(integers()), lambda children: lists(children) | children)


@given(alist=nested_lists)
def test_regular_list(alist):
    flat = Flatten(alist).to_list()

    for elem in flat:
        assert isinstance(elem, int)


def test_fixed_example():
    alist = [[2,3,[4,5],6],7,8,[[2,3],[5,6]]]

    flat = Flatten(alist).to_list()

    assert flat == [2,3,4,5,6,7,8,2,3,5,6]