Add a maxsplit, reverse parameters to split_

[jferard]

maxsplit

more-itertools has various split_ functions (split_at, split_after, split_before, split_when, split_into) but none of these functions has a way to stop the split after a given number of elements. Of course, we can take the first elements of a split_... iterator and swtich to the original iterator:

>>> import more_itertools as mi, itertools
>>> s = '0,1,2,3,4,5,6,7,8,9'
>>> it1 = iter(s)
>>> it2 = mi.split_after(it1, lambda x: x == ",")
>>> list(itertools.islice(it2, 3)) # it *2*
[['0', ','], ['1', ','], ['2', ',']]
>>> list(it1) # it *1*
['3', ',', '4', ',', '5', ',', '6', ',', '7', ',', '8', ',', '9']

But it would be more convenient to write, as we do with str.split:

>>> import more_itertools as mi, itertools
>>> s = '0,1,2,3,4,5,6,7,8,9'
>>> it2 = mi.split_after(s, lambda x: x == ",", maxsplit=3)
>>> list(it2) # it *2*
[['0', ','], ['1', ','], ['2', ','], ['3', ',', '4', ',', '5', ',', '6', ',', '7', ',', '8', ',', '9']]

(The last parameter could be an iterator to remain lazy).

reverse

We could have another parameter, named reverse to mimic str.rsplit:

>>> it2 = mi.split_after(s, lambda x: x == ",", maxsplit=3, reverse=True)
>>> list(it2) # it *2*
[['0', ',', '1', ',', '2', ',', '3', ',', '4', ',', '5', ',', '6', ','], ['7', ','], ['8', ','], ['9']]

(Or create rsplit_at, rsplit_after, ... but that would be a little cumbersome)

Implementation should not be difficult.

[bbayles]

I'd entertain a PR for the maxsplit additions, and a separate one for reverse.

[jferard]

@bbayles Would you allow:

• a keep_separator parameter for split_at (useful for the implementation)
• the name rsplit for the parameter instead of reverse because reverse might be confusing
  ?

Examples (handwritten):

>>> list(mi.split_at("a,bc,def", lambda c: c==',', keep_separator=True))
[['a'], [','], ['bc'], [','], ['def']]

>>> list(mi.split_at("a,bc,def", lambda c: c==',', maxsplit=1, rsplit=True))
[['a,bc'], ['def']]