Python中带双下划线是什么意思，例如__next__()以及__name__

__next__()
__main__
__name__

例如这些有很多很多，他们代表什么意思？

参考这个：
https://blog.csdn.net/weixin_39602571/article/details/111450576?ops_request_misc=%257B%2522request%255Fid%2522%253A%2522165029317816780255227414%2522%252C%2522scm%2522%253A%252220140713.130102334.pc%255Fblog.%2522%257D&request_id=165029317816780255227414&biz_id=0&utm_medium=distribute.pc_search_result.none-task-blog-2~blog~first_rank_ecpm_v1~rank_v31_ecpm-1-111450576.nonecase&utm_term=Python%E4%B8%AD%E5%B8%A6%E5%8F%8C%E4%B8%8B%E5%88%92%E7%BA%BF%E6%98%AF%E4%BB%80%E4%B9%88%E6%84%8F%E6%80%9D&spm=1018.2226.3001.4450
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