Difference between revisions of "AGGREGATE world"

Revision as of 13:22, 16 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)

Country Profile

For these questions you should use aggregate([]) on the collection world

Give the name and the per capita GDP for those countries with a population of at least 200 million.

per capita GDP is the GDP divided by the population GDP/population

pp.pprint(list(
    db.world.aggregate([
        {"$match":{
            "population":{"$gte":250000000}
        }},
        {"$project":{
            "_id":0,
            "name":1,
            "per capita GDP": {"$divide": ["$gdp",1000000]}
        }}
    ])
))

pp.pprint(list(db.world.aggregate([{"$match":{"population":{"$gte":200000000}}},{"$project":{"_id":0,"name":1,"per capita GDP": {"$divide": ["$gdp","$population"]}}}])))

@@ Line 21: / Line 21: @@
 <div class="hint" title="How to calculate per capita GDP">
 per capita GDP is the GDP divided by the population GDP/population
-</div>
-<div class="hint" title="Using the aggregation framework">
-The aggregation framework is a data processing pipeline. There are many operators that you can use.<br/>
-<code>$match</code> uses a query to limit or 'filter' what documents are to be used in the next stage of the pipeline.<br/>
-<code>$project</code> is used to "shape" documents by adding or removing fields. It also allows you to compare fields with the syntax $<fieldname>
 </div>
 <pre class=def>
@@ Line 42: / Line 36: @@
 ))
 </pre>
-<div class=ans>
+<div class=ans>pp.pprint(list(db.world.aggregate([{"$match":{"population":{"$gte":200000000}}},{"$project":{"_id":0,"name":1,"per capita GDP": {"$divide": ["$gdp","$population"]}}}])))
-pp.pprint(list(
-    db.world.aggregate([
-        {"$match":{
-            "population":{"$gte":200000000}
-        }},
-        {"$project":{
-            "_id":0,
-            "name":1,
-            "per capita GDP": {"$divide": ["$gdp","$population"]}
-        }}
-    ])
-))
 </div>
 </div>