在PyMongo中使用.sort - Python 实用宝典

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问题：在PyMongo中使用.sort

使用PyMongo，当我尝试检索按其“数字”和“日期”字段排序的对象时，如下所示：

db.test.find({"number": {"$gt": 1}}).sort({"number": 1, "date": -1})

我收到此错误：

TypeError: if no direction is specified, key_or_list must be an instance of list

我的排序查询出了什么问题？

With PyMongo, when I try to retrieve objects sorted by their ‘number’ and ‘date’ fields like this:

db.test.find({"number": {"$gt": 1}}).sort({"number": 1, "date": -1})

I get this error:

TypeError: if no direction is specified, key_or_list must be an instance of list

What’s wrong with my sort query?

sort 应该是键方向对的列表，即

db.test.find({"number": {"$gt": 1}}).sort([("number", 1), ("date", -1)])

之所以必须是列表，是因为参数的顺序很重要，而dicts在Python <3.6中不排序

sort should be a list of key-direction pairs, that is

db.test.find({"number": {"$gt": 1}}).sort([("number", 1), ("date", -1)])

The reason why this has to be a list is that the ordering of the arguments matters and dicts are not ordered in Python < 3.6