如何使用嵌套 for 循环创建嵌套列表？

Question

    def remove_extras(self, paths, destination):
        # Delete all paths that does not include the destination
        destination_paths = []
        destination_path = []
        for path in paths:
            if destination in path:
                for router in path:
                    destination_path.append(router)
                destination_paths.append(destination_path)
        print(destination_paths)

        return destination_paths[1:]

why am I getting [[router, router, router, ....]] and not [[router, router, ...], [router, router, ...], .....]?

Answer 1

I think you overlooked that you are appending routers to the same destination_path list object all the time - then after the inner for-loop you are appending the same destination_path list object multiple times to destination_paths .

Instead, you should move the definition of destination_path inside the outer for loop - the code would then look like this:

    def remove_extras(self, paths, destination):
        # Delete all paths that does not include the destination
        destination_paths = []
        for path in paths:
            if destination in path:
                destination_path = []
                for router in path:
                    destination_path.append(router)
                destination_paths.append(destination_path)
        print(destination_paths)

        return destination_paths[1:]

Answer 2

Without even knowing what you would like to achieve, the previous posted code was almost right. Try this one here:

def remove_extras(self, paths, destination):
    destination_paths = []
    for path in paths:
        destination_path = []
        if destination in path:
            for router in path:
                destination_path.append(router)
    
        destination_paths.append(destination_path)
    
    return destination_paths