2019 年 stackoverflow 网站最受欢迎的 20 个 Python 问题

在最新一期的“Python开发者周刊”（Pycoder's weekly）里，我看到一则有意思的分享，故转出来分享给你们。

该分享来自是一份”python weekly reports“，统计了 2019 年里 stackoverflow 网站上支持数最高的 20 个问题。问题列表以下（方括号中的两个数字是其支持数与回答数）：

1. Why does Python's hash of infinity have the digits of π? - [236/3]
2. Is there a more elegant way to express ((x == a and y == b) or (x == b and y == a))? - [105/10]
3. Why can I use a list index as an indexing variable in a for loop? - [92/6]
4. Why does (inf + 0j)*1 evaluate to inf + nanj? - [93/4]
5. Why is f'{{{74}}}' the same as f'{{74}}' with f-Strings? - [88/1]
6. Why does b+=(4,) work and b = b + (4,) doesn't work when b is a list? - [75/7]
7. Why does Python start at index -1 (as opposed to 0) when indexing a list from the end? - [79/7]
8. Why is TensorFlow 2 much slower than TensorFlow 1? - [104/2]
9. Randomness of Python's random - [70/4]
10. Why does Python allow out-of-range slice indexes for sequences? - [72/2]
11. Unexpected behaviour with Python generator - [57/8]
12. What exactly is meant by "partial function" in functional programming? - [55/3]
13. What does a yield inside a yield do? - [56/4]
14. Issues implementing the "Wave Collapse Function" algorithm in Python 2.7 - [52/2]
15. Should linear read-shuffled write always be faster than shuffled read-linear write? (Was: Why is fancy assignment slower than fancy lookup?) - [53/5]
16. How to write 2**n - 1 as a recursive function? - [49/7]
17. Why is a for loop so much faster to count True values? - [53/5]
18. Is there a difference between board[x, y\] and board[x][y] in Python? - [47/6]
19. Why was p[:] designed to work differently in these two situations?- [51/6]
20. Jupyter notebook: No connection to server because websocket connection fails - [46/4]

不用怀疑，这些内容的支持数和回答数就是那么少。不过也需注意，它统计的是问题自己的支持数，而不是回答的支持数（尽管回答的支持数也不多）。

还有一点需注意，这份报告并不是 stackoverflow 网站的官方报告，并且文中也未说明统计口径与筛选标准，因此咱们姑且一看。

有些问题可能挺怪的，或者平时不大可能考虑到，好比关于列表的两个问题：为何从列表末尾查找时是从 -1 开始？为何列表的切片容许越界？

很多回答都挺有专业精神，每每会带来新的视角和知识信息。好比，关于列表的 -1 索引问题，高票回答中提到了“~”运算符，有这样的用法：

arr = ["a", "b", "c", "d"]
print(arr[~0])   # d
print(arr[~1])   # c

让人眼前一亮！

还有一个问题是：如何优雅地计算 ((x == a and y == b) or (x == b and y == a)) 这个形式的结果？

高票回答是这样：

初一看，就像看人变戏法同样……

其它问题和回答就不一一说明了，建议感兴趣的同窗按图索骥，循序渐进，顺藤摸瓜，顺手牵羊……

连接清单：

https://python-weekly.blogspot.com/2020/01/20-best-python-questions-at.html?m=1

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