PYTHON在每个组中选择最低分

Question

我在我的数据库中有一个名为“item”的对象，我想写一些python，它将从每组student_id中选择最低分数....我是一个总数蟒蛇noob ...我怎么做到这一点？有

运行我的代码一些麻烦......我可以得到一些健全检查完成：

{u'student_id': 197, u'_id': ObjectId('50906d7fa3c412bb040eb88d'), u'type': u'homework', u'score': 10.90872422518918} 
{u'student_id': 197, u'_id': ObjectId('50906d7fa3c412bb040eb88e'), u'type': u'homework', u'score': 88.3871242475841} 
{u'student_id': 198, u'_id': ObjectId('50906d7fa3c412bb040eb892'), u'type': u'homework', u'score': 17.46279901047208} 
{u'student_id': 198, u'_id': ObjectId('50906d7fa3c412bb040eb891'), u'type': u'homework', u'score': 76.18366499496366} 
{u'student_id': 199, u'_id': ObjectId('50906d7fa3c412bb040eb895'), u'type': u'homework', u'score': 49.34223066136407} 
{u'student_id': 199, u'_id': ObjectId('50906d7fa3c412bb040eb896'), u'type': u'homework', u'score': 58.09608083191365} 

更新？我得到这个错误...

NameError: name 'getResultFromDatabase' is not defined 

谢谢你的麻烦....这里是我的代码...

import pymongo 

from itertools import groupby 
from pymongo import Connection 

data = getResultFromDatabase() 
connection = Connection('localhost', 27017) 

db = connection.students 

item = db.grades.find({'type' : 'homework'}).sort([('student_id',pymongo.ASCENDING),('score',pymongo.ASCENDING)]) 



for id, items in groupby(data, lambda s: s['student_id']): 
    lowest_score = min(i['score'] for i in items) 

    print lowest_score 

Answer 1

groupby你想要做什么：

from itertools import groupby 

data = getResultFromDatabase() 

for id, items in groupby(data, lambda s: s['student_id']): 
    lowest_score_entry = min(items, key=lambda i: i['score']) 
    print lowest_score_entry['score'], lowest_score_entry['_id']