Difference between revisions of "Sort"

Revision as of 14:42, 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.

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

@@ Line 20: / Line 20: @@
 The aggregation framework provides the <code>$sort</code> operator, and <code>map_reduce</code> takes sort as a parameter that is applied to the input documents.<br/><br/>
 The syntax for <code>sort()</code> is <code>sort(<field>:<value>)</code> where 1 indicates ascending and -1 indicates descending.<br/>
-The order in which fields are specified dictates which fields are sorted first.
+The order in which fields are specified dictates which fields are sorted first.<br/><br/>
+Python does not store key order for dicts, so instead of the mongo shell <code>{<field1>:<value>,<field2>:<value>}</code> use <code>[(<field1>,<value>), (<field2>,<value>)]</code>
 </div>
@@ Line 26: / Line 27: @@
 <pre class=def>
 pp.pprint(list(
-     db.world.find().sort({"population":-1,"name":1}))
+     db.world.find().sort([("population",-1),("name",1)])
 ))
 </pre>
 </div>