MongoDB Aggregation Python Class

MongoDB/aggregate.py is moudle for MongoDB Aggregation,it change operation easy and readable.

1,Class Pipeline(): construct pipeline for MongoDB Aggregation,such as $match,$group,$limit,unwind.... Note: sometimes you need special key, like '$id' or 'eventValue.subValue',but '$','.' is invalid in **kwargs's key. you should use '' replace '$",use '' replace '.' in this class and there is a method 'def __recover(self,arg)',could recoverd.

Example:

p = Pipeline()
p.limit(___limit=1000).match(city="Beijing",year__month=4).group(_id="$city",spots={"$push":"spot"})
print p.get()

you will get:
[{'$limit': 1000}, {'$match': {'city': 'Beijing', 'year.month': 4}}, {'$group': {'_id': '$city', 'spots': {'$push': 'spot'}}}]

2,method aggregate(collection,pipeline,*keys) : excute collection.aggregate(pipeline) and return need lists with keys. Example:

  result_list = aggregate(collection,pipeline,'users')

you will get a list as key = 'users' after  aggregate the pipeline on collection.
when you need more than one key's list, you can:
  result_list = aggregate(collection,pipeline,'users','messages',...)