PyCharming

PythonIterating.py

import pymongo
import sys

# Connect
connection = pymongo.MongoClient("mongodb://localhost")

# Fondle
db = connection.school
grades = db.school.students

## Feeling a little loopy today. Looking at this problem I was given.
## Remove lowest items from a mongodb database.


# I'm in the mood to unwind.

# I need a unique student_id and the lowest grade. So, for example, I need all student_id 9.
# Now I know data can also get the lowest here, but I don't know... do I want the lowest grade with this function?
# Or do I just want the student? Hrm...
# To hell with it - we'll get the lowest value here.
def lowest_grade(student_id, score):

    query = {"_id": student_id, "scores": score}

    # Jeez. Nothing's simple with me.
    print "Searchin' query: %s" % query

    try:

        cursor = grades.find(query)
        #cursor = cursor.limit(1)
        #cursor = cursor.sort([('scores.score', pymongo.ASCENDING)])

    except Exception as e:
        print "Unexpected error:", type(e), e

    for doc in cursor:
        print doc, ' ', id



# Iterate through the students and print their ids or whatever.
def sort_the_students(type):

    query = {"name" : "Bao Ziglar"}
    #I am so grateful for the unwind function. Nothing like a nice bottle of whine during an aggregation lesson.

    # Jeez. Nothing's simple with me.
    #print "Searchin' query: %s" % query

    try:

        cursor = db.students.aggregate([ {'$unwind': '$scores'} ] )
        #print cursor.next()
        investing_id = db.students.aggregate([ {'$unwind': '$scores'} ] ).next()['_id']
        count = 0
        score = db.students.aggregate([ {'$unwind': '$scores'} ] ).next()['scores']['score']
        #print investing_id , " ", scorey
        selected = "null"
        scores = []
    except Exception as e:
        print "Expected error:", type(e), e

    for doc in cursor:
        if doc['scores']['type'] == 'homework':
          if investing_id == doc['_id']:
            if count != 0:
                homework = doc['scores']
                #print "kalika:", score, doc['scores']['score'], doc['_id']
                #if doc['scores']['score'] < score:
                if doc['scores']['score'] > score:
                    selected = doc['scores']['score']
                else:
                    selected = score
                #print "kalika:", selected, doc['_id']
                homework['score'] = selected
                homework['type'] = "homework"
                #if doc['scores']['score'] == selected:
                    #print doc
                    #doc.explain()
                 #   homework = doc['scores']
                #else:
                    #print "kalika:", selected, doc['_id']
                 #   homework = doc['scores']
                  #  homework['score'] = selected
                #delete one document from students.scores where homework docid = doc_id, type = homework, and score = selected.
                #lowest_grade(doc['_id'], selected)
                #print investing_id , ": " , homework
                scores.append(homework)
                print scores , " ID ", doc['_id']
                #print db.students.find_one({ "_id" : doc['_id']})
                results = db.students.update({"_id": doc['_id']}, { "$set" : { "scores" : scores}})
                print results
                scores = []
                #Set the score with the selected value to 0, make sure that type = homework.

                #query = {"_id" : doc['_id'] }
                #consider adding index to scores documents.
                #print db.students.find( {"_id": doc['_id']}, { "scores" : { "$elemMatch" : { "score" : selected, type: "homework"  } } } )
                #print db.students.aggregate( [ { "$match": { "_id" :doc['_id'], "scores": { "$elemMatch": { "score" : selected, "type": "homework"  } } } } ] ).next()
                #db.students.aggregate([{ $match: {_id: 0, scores: {$elemMatch: {score: 35.8740349954354, type: "homework"}}}}, { $redact: "$PRUNE"}] ).next()
                #db.students.aggregate( [ { $match: { _id:0, scores: {$elemMatch: { score : 35.8740349954354, type: "homework"  } } } }, { $redact: { $cond: { if: { $eq: ["$type", "homework"] }, then: "$$PRUNE", else: "$$DESCEND" } } } ] )
                #db.students.aggregate([{ $match: {_id: 0, scores: {$elemMatch: {score: 35.8740349954354, type: "homework"}}}}, { $redact: { $cond: { if: { $eq: ["$type", "homework"]}, then: "$$KEEP", else: "$$DESCEND"}}}] )
                # db.students.aggregate( [ { $match: { _id:0, scores: {$elemMatch: { score : 35.8740349954354, type: "homework"  } } } }, { $redact: { $cond: { if: { $gt: [ { $size: { $setIntersection: [ "$type", ["homework"]] } }, 0 ] }, then: "$$KEEP", else: "$$DESCEND" } } } ] )
               # db.students.aggregate([{ $match: {_id: 0, scores: {$elemMatch: {score: 35.8740349954354, type: "homework"}}}}, { $redact: { $cond: { if: { $gt: [{ $spot: { $setIntersection: ["$type", ["homework"]]}}, 0]}, then: "$$KEEP", else: "$$DESCEND"}}}] )
               #db.students.aggregate( [ { $match: { _id:0, scores: {$elemMatch: { score : 35.8740349954354, type: "homework"  } } } }, { $redact: { $cond: { if: { $gt: [ { spot: { $setIntersection: [ "$type", ["homework"] ] } }, 0 ] }, then: "$$KEEP", else: "$$DESCEND" } } } ] )
                #db.students.aggregate([ {'$unwind': '$scores'}, {$sort: {scores:{ $meta: "type" } } } ] )
                #Can use this one, there's more than one of each type of score.
                #db.students.aggregate([{ $match: {_id: 0, scores: {$elemMatch: {score: 35.8740349954354}}}}, { $redact: { $cond: { if: { $eq: ["$type","homework"]}, then: "$$PRUNE", else: "$$DESCEND"}}}] )



                count = count + 1
            else:
                count = count + 1
            #if  doc['scores']['score'] <= score:
            if doc['scores']['score'] >= score:
               score = doc['scores']['score']
               #print "Selected: ", doc
          else:
             #score = 760
             score = doc['scores']['score']
             #print doc['_id'] , " ", scores
             #scores = []
           #goodbye = grades.delete_one({'_id': doc['_id']})
             #$result = db.schoo
             #db.collection.update( {_id:doc['id']}, {$set: { scores: scores} } )
             #print scores
           #print goodbye

          #count = count + 1
          investing_id = doc['_id']
          #print doc["scores"]
        else:
            #print doc
            scores.append(doc['scores'])
            #scores.append["3"]
        #investing_id = doc['_id']
        #print "Scores: ", scores
    print count - 1

sort_the_students("homework")
#replace_the_scores(scores)
#lowest_grade(199,  { "type" : "homework", "score" : 5.861613903793295 })

Gist example.

Working with Python and Mongo; aka PyMongo and committing to memory: how to connect to a database, how to aggregate and how to unwind.

Especially useful for understanding the cursor.