Python有SQL中group by推导吗，pythongroup,现查询基于mongoen

Python有SQL中group by推导吗，pythongroup,现查询基于mongoen

现查询基于mongoengine的文档，其结构如下：

#课程分类class Category(EmbeddedDocument):    name=StringField()#课程class Course(Document):    title=StringField()    category=EmbeddedDocumentField(Category)

现假定有若干分类，及若干课程文档，有没有简洁的办法查询出去重的课程分类名称，及该类课程的总数？比如：

[    ('课程类型1',25),    ('课程类型2',10),    ('课程类型3',20),    ...]

from operator import itemgetterfrom itertools import groupbylst = [dict(category=c.category.name, title=c.title) for c in Course.objects]lst.sort(key=itemgetter('category'))categories = [(category, len(list(items))) for category, items in groupby(lst, key=itemgetter('category'))]

编橙之家文章，