小编lui*_*iel的帖子

我开始学习Python(python 3.3),我正在尝试is运算符.我试过这个:

>>> b = 'is it the space?'
>>> a = 'is it the space?'
>>> a is b
False
>>> c = 'isitthespace'
>>> d = 'isitthespace'
>>> c is d
True
>>> e = 'isitthespace?'
>>> f = 'isitthespace?'
>>> e is f
False

似乎空间和问号使is行为表现不同.这是怎么回事？

编辑:我知道我应该使用==,我只是想知道为什么is会这样.

如果我只能找到它的位置,我确信这是一个很容易修复的错误.这是Flask应用程序的错误:

11:58:18 web.1  | ERROR:xxxxxx.core:Exception on / [GET]
11:58:18 web.1  | Traceback (most recent call last):
11:58:18 web.1  |   File "/Library/Python/2.7/site-packages/flask/app.py", line 1817, in wsgi_app
11:58:18 web.1  |     response = self.full_dispatch_request()
11:58:18 web.1  |   File "/Library/Python/2.7/site-packages/flask/app.py", line 1477, in full_dispatch_request
11:58:18 web.1  |     rv = self.handle_user_exception(e)
11:58:18 web.1  |   File "/Library/Python/2.7/site-packages/flask/app.py", line 1381, in handle_user_exception
11:58:18 web.1  |     reraise(exc_type, exc_value, tb)
11:58:18 web.1  |   File "/Library/Python/2.7/site-packages/flask/app.py", line 1475, in full_dispatch_request
11:58:18 web.1  |     rv = self.dispatch_request()
11:58:18 web.1  |   File …

我正在尝试这样做:

event = coll.find_one({"_id": {"$oid": event_id}})

其中event_id是ObjectId中的字符串:

event_id='50bbd48eefbdd2a1e83bc440'

但事件最终是空的.我确定这不是你在pymongo中用ObjectId找到文件的方式,但是我已经搜索了一段时间并且没有弄清楚如何.任何帮助,将不胜感激.谢谢!