在python中的字符串mongo查询中传递参数

Question

I have following query in my database

query = u'collection.aggregate([{ "$match": { "code": { "$in": {__sensors__}} } },{"$project" : {"_id" : 0}},{"$group" : {"_id": "$code", "data": {"$last": "$$ROOT"}}}])'

And I have following arguments, Now I want to pass that argument in the above query.

args = {"__sensors__": ["GP0", "GP1", "GP5", "GP6"]}

I'm trying following but it is giving me an error.

query.format(**args)

above statement giving me this error

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-44-7db1aba33ea5> in <module>()
----> 1 a.query.format({"__sensors__": []})

KeyError: u' "$match"'

Can anyone give me the solution for the above problem?

Answer 1

Your problem is because of the { and } . When you use them in format python thinks that maybe that is a variable. So to fix that you need to make it double. Like below:

query = u'collection.aggregate([{{ "$match": {{ "code": {{ "$in": {__sensors__}}} }} }},{{"$project" : {{"_id" : 0}}}},{{"$group" : {{"_id": "$code", "data": {{"$last": "$$ROOT"}}}}}}])'

As you see I didn't double the {__sensors__} . Because your're going to replace it in the query.format(**args) line.

The final result would be like this:

'collection.aggregate([{ "$match": { "code": { "$in": [\'GP0\', \'GP1\', \'GP5\', \'GP6\']} } },{"$project" : {"_id" : 0}},{"$group" : {"_id": "$code", "data": {"$last": "$$ROOT"}}}])'