爬取 Stackoverflow 100万条问答

作为一个热爱编程的大学生，怎么能不知道面向stackoverflow编程呢。

打开stackoverflow主页，在questions页面下选择按vote排序，爬取前20000页，每页将问题数量设置为50，共100W条，（实际上本来是想爬完1300W条的，但100W条后面问题基本上都只有1个或0个回答，那就选取前100W就好吧）

对爬取数据进行简单分析

降序排列了这100W条数据的votes数，生成折线图

2k后的问题的votes数基本上就已经在400以下了，接着后面的就基本上是贴地飞行了
votes数最多 : Why is it faster to process a sorted array than an unsorted array?

votes数的连续分布情况

可见最多的还是集中在1-2K之间,从6k开始基本上就断层了

降序排列了这100W条数据的answers数，生成折线图

很明显2k之后的answers数基本上就小于20条了
answers数最多: What is the best comment in source code you have ever encountered? [closed]

answers数的连续分布情况

150后也就断层了，实际上能达到这样的回答数极少

降序排列了这100W条数据的views数，生成折线图

最高达到了4.5m，10000以后的基本上就不足3000了
views数最多: How to undo last commit(s) in Git?

views数的连续分布情况

再看看votes，views，answers三者的散点图对应情况

votes - views

votes - answers

views - answers

总的来说，这三者对应关系类似于一个金字塔。三个图基本上都是左下角靠近原点的区域被填满，也就是说绝对大部分的问题的votes，answers和views都是属于最下层的。高质量活跃的问题是处于金字塔顶端的。三者的最高数好像也没特别明显的对应关系，且三者的最高数都不是同一个问题。

根据所有问题的tags提取出总量前200的关键词（前50条如下），第1名是c#，python排在第5

('c#', 94614),
('java', 93244),
('javascript', 76722),
('android', 69321),
('python', 62502),
('c++', 58173),
('php', 42596),
('ios', 37773),
('jquery', 37405),
('.net', 36180),
('html', 28536),
('css', 26174),
('c', 24699),
('objective-c', 23253),
('iphone', 22171),
('ruby-on-rails', 20143),
('sql', 19171),
('asp.net', 18060),
('mysql', 17559),
('ruby', 16397),
('r', 15670),
('git', 13139),
('linux', 13080),
('asp.net-mvc', 12857),
('angularjs', 12606),
('sql-server', 12473),
('node.js', 12212),
('django', 11576),
('arrays', 11006),
('algorithm', 10959),
('wpf', 10631),
('performance', 10619),
('xcode', 10613),
('string', 10426),
('windows', 10132),
('eclipse', 10117),
('scala', 9942),
('regex', 9685),
('multithreading', 9601),
('json', 9266),
('swift', 8950),
('c++11', 8939),
('haskell', 8823),
('osx', 8159),
('visual-studio', 8140),
('html5', 7627),
('database', 7567),
('xml', 7478),
('spring', 7464),
('unit-testing', 7253),
('bash', 6825)

这样看好像不太直观，所以就把它根据词频生成了词云

因为是用python写的爬虫，所以重点来分析下Python类的问答

votes数前10

• votes数
• 6162 : What does the “yield” keyword do in Python?
• 3529 : What is a metaclass in Python?
• 3098 : How do I check whether a file exists using Python?
• 3035 : Does Python have a ternary conditional operator?
• 2620 : Calling an external command in Python
• 2605 : What does if name == “main”: do?
• 2194 : How to merge two Python dictionaries in a single expression?
• 2123 : Sort a Python dictionary by value
• 2058 : How to make a chain of function decorators?
• 1984 : How to check if a directory exists and create it if necessary?

answers数前10

• answers数
• 191 : Hidden features of Python [closed]
• 87 : Best ways to teach a beginner to program? [closed]
• 55 : Favorite Django Tips & Features?
• 50 : How do you split a list into evenly sized chunks?
• 44 : Calling an external command in Python
• 43 : How can I represent an 'Enum' in Python?
• 38 : How to merge two Python dictionaries in a single expressions
• 38 : Finding local IP addresses using Python's stdlib
• 37 : Reverse a string in python without using reversed or [::-1]
• 37 : How do I check whether a file exists using Python?

views数前10

• views数
• 2121621 : Parse String to Float or Int
• 1905938 : Using global variables in a function other than the one that created them
• 1888666 : How do I check whether a file exists using Python?
• 1827126 : Calling an external command in Python
• 1699574 : Converting integer to string in Python?
• 1686230 : How do I read a file line-by-line into a list?
• 1682307 : Iterating over dictionaries using 'for' loops in Python
• 1569205 : How to get the size of a list
• 1554755 : How do I install pip on Windows?
• 1515505 : Finding the index of an item given a list containing it in Python

三者的前十中有两个问题是完全重叠的，分别是

• How do I check whether a file exists using Python?
• Calling an external command in Python

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