Difference between revisions of "AGGREGATE world"

Revision as of 13:35, 17 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.

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"]}}}])))

Give the name and the population density of all countries. Ignore results where the density is "None".

population density is the population divided by the area

Use a $match. {"area":{"$ne":0}}


pp.pprint(list(
    db.world.aggregate([
        {"$project":{
            "_id":0,
            "name":1,
            "density": {"$divide": [10000,"$area"]}
        }},
        {"$match":{
            "density": {"$ne":None}
        }}
    ])
))


pp.pprint(list(db.world.aggregate([{"$match":{"area":{"$ne":0}}},{"$project":{"_id":0,"name":1,"density":{"$divide":["$population","$area"]}}},{"$match":{"density":{"$ne":None}}}])))


Show the name and population in millions for the countries of the continent South America. Divide the population by 1000000 to get population in millions. 

pp.pprint(list(
    db.world.aggregate([
        {"$match":{
            
        }},
        {"$project":{
            "_id":0
        }}
    ])
))


pp.pprint(list(

   db.world.aggregate([
       {"$match":{
           "continent": {"$eq":"South America"}
       }},
       {"$project":{
           "name": 1,
           "population": {"$divide": ["$population",1000000]}
       }}
   ])

))

@@ Line 18: / Line 18: @@
 <div class='extra_space' style='width:1em; height:6em;'></div>
 <div class=q data-lang="py3">
-<p class=strong>
 Give the <code>name</code> and the <code>per capita GDP</code> for those countries with a <code>population</code> of at least 200 million.
-</p>
 <div class="hint" title="How to calculate per capita GDP">
 per capita GDP is the GDP divided by the population.
@@ Line 43: / Line 41: @@
 <div class=q data-lang="py3">
-Give the <code>name</code> and the <b>population density</b> of all countries. Ignore results where the density is "None".
+Give the <code>name</code> and the <code>population density</code> of all countries. Ignore results where the density is "None".
 <div class="hint" title="How to calculate population density">
 population density is the population divided by the area
@@ Line 70: / Line 68: @@
 <div class=q data-lang="py3">
+Show the <code>name</code> and <code>population</code> in millions for the countries of the continent <b>South America</b>. Divide the population by 1000000 to get population in millions.
 <pre class=def>
+pp.pprint(list(
+    db.world.aggregate([
+        {"$match":{
+        }},
+        {"$project":{
+            "_id":0
+        }}
+    ])
+))
 </pre>
 <div class=ans>
+pp.pprint(list(
+    db.world.aggregate([
+        {"$match":{
+            "continent": {"$eq":"South America"}
+        }},
+        {"$project":{
+            "name": 1,
+            "population": {"$divide": ["$population",1000000]}
+        }}
+    ])
+))
 </div>
 </div>