Python group_when(predicate, iterable) function

group_when.py

def group_when(pred, iterable):
    """Yield groups (as lists), starting a new group when pred(item) is True.
    
    The predicate is ignored for the first item in iterable, which always starts
    a new group.
    
    Args:
        pred: A predicate function used to determine when a new group
             should be started.
             
        iterable: Any iterable series of objects which can be passed to pred().
        
    Yields:
        Lists of grouped items in the same order as from iterable.
    """
    
    iterator = iter(iterable)

    try:
        group = [next(iterator)]
    except StopIteration:
        return

    for item in iterator:
        if pred(item):
            yield group
            group = []
        group.append(item)
        
    if group:
        yield group