Difference between revisions of "Sort"

Revision as of 13:42, 27 July 2015

#ENCODING
import io
import sys
sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-16')
#MONGO
from pymongo import MongoClient
client = MongoClient()
client.progzoo.authenticate('scott','tiger')
db = client['progzoo']
#PRETTY
import pprint
pp = pprint.PrettyPrinter(indent=4)
#CODE
from bson.code import Code

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sort() is a cursor method that orders the results of a query.
The aggregation framework provides the $sort operator, and map_reduce takes sort as a parameter that is applied to the input documents.

The syntax for sort() is sort(<field>:<value>) where 1 indicates ascending and -1 indicates descending.
The order in which fields are specified dictates which fields are sorted first.

Python does not store key order for dicts, so instead of the mongo shell {<field1>:<value>,<field2>:<value>} use [(<field1>,<value>), (<field2>,<value>)]

Sort all the documents in world by population descending, then name ascending. Show only name and population.

pp.pprint(list(
    db.world.find().sort([("population",-1),("name",1)])
))

@@ Line 24: / Line 24: @@
 </div>
-<div class=q data-lang="py3">Sort all the documents in world by population descending, then name ascending.
+<div class=q data-lang="py3">Sort all the documents in world by population descending, then name ascending. Show only name and population.
 <pre class=def>
 pp.pprint(list(