Merging Iterables with Fillvalue Using zip_longest

This function is used to merge multiple iterable objects. If the length of the iterators is not consistent, fillvalue is used as the filling value.

Technology Stack : collections, itertools

Code Type : Function

Code Difficulty : Advanced

                
                    
def zip_longest(*iterables, fillvalue=None):
    # 从内置库collections中选取的zip_longest函数用于合并多个可迭代对象，并填充缺失值
    from collections import deque
    from itertools import zip_longest as zip_longest_itertools

    def iter_from_queue(queue):
        for item in queue:
            if isinstance(item, deque):
                for subitem in iter_from_queue(item):
                    yield subitem
            else:
                yield item

    queue = [deque(iterable) for iterable in iterables]
    for _ in range(max(len(q) for q in queue)):
        for q in queue:
            if q:
                yield q.popleft()
    while queue:
        for q in queue:
            if q:
                yield q.popleft()
                break

    return zip_longest_itertools(*queue, fillvalue=fillvalue)