This is the only quasi-legitmiate use I have found for the while..else construct in Python.

while_else.py

def pop_count_until(stack, predicate):
    """Count the number of items which need to be popped off a stack
    for the top item to satisfy a predicate.

    The stack argument is modified by this call. If the return value is
    non-negative the top item on the stack will satisfy the predicate
    on return.

    Args:
        stack: Any object supporting:
            item = stack.pop()  # Remove and return the top item
            stack.append(item)  # Push an item to the top
            if stack:           # False in a boolean context when empty

        predicate: A predicate used for testing items to be popped off the stack.

    Returns:
        The number of items which were popped off the stack before the
        top item satisfied the predicate, if such an item was present in the
        stack, otherwise -1.
    """
    count = 0
    while stack:
        item = stack.pop()
        if predicate(item):
            stack.append(item)
            break
        count += 1
    else:
        count = -1
    return count