groupreduce.py

def groupreduce(iterable, groups, is_part_of_group, add_item_to_group):
    """
    Reduces a sorted iterable into groups.

    >>> iterable = iter((1, 2, 8, 12, 32, 35))
    >>> groups = (10, 20, 30, 40, 50)
    >>>
    >>> def is_part_of_group(group_id, item):
    >>>     return group_id-10 <= item < group_id
    >>>
    >>> def add_item_to_group(group_obj, item):
    >>>     if group_obj is None:
    >>>         group_obj = []
    >>>     if item is not None:
    >>>         group_obj.append(item)
    >>>     return group_obj
    >>>
    >>> for group in groupreduce(iterable, groups, is_part_of_group,
    >>>                          add_item_to_group):
    >>>     print(group)
    [1, 2, 8]
    [12]
    []
    [32, 35]
    []
    """

    last_item = None
    for group in groups:
        group_obj = None
        while True:
            if last_item:
                item = last_item
                last_item = None
            else:
                try:
                    item = next(iterable)
                except StopIteration:
                    item = None
                    break
            if is_part_of_group(group, item):
                group_obj = add_item_to_group(group_obj, item)
            else:
                last_item = item
                break
        if group_obj is None:
            group_obj = add_item_to_group(None, None)
        yield group_obj