View source for FIND basics


<pre class=setup>
#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)
</pre>

==Working with the <code>world</code> collection of countries==
  <p>This tutorial introduces NoSQL using MonogDB and PyMongo under Python3.4. We will be using the <code>find()</code> command and comparison functions on the collection '''world''' which contains details of around 250 countries of the world:</p>
[[FIND examples]] are available.
<div class='extra_space' style='width:1em; height:6em;'></div>
<div class=q data-lang="py3">
Use <code>find()</code> to return the 21st document in world
<p class=strong>Show the 21st document in world</p>
<pre class=def>
pp.pprint(
    db.world.find()[0]
)
</pre>
<div class=ans>
pp.pprint(db.world.find()[20])
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>List all the countries in the continent of Asia</p>
<pre class=def>
pp.pprint(list(
  db.world.find({},{"capital":1, "_id":0})
))
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"continent":"Asia"}, {"_id":0, "name":1})))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>How many countries are there in Europe that start with the letter "L"</p>
<pre class=def>
</pre>
<div class=ans>
print(db.world.count({"$and":[{"continent":"Europe"},{"name":{"$regex":"^S"}}]}))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Find the capital cities for countries with a population of over 70 million</p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"population":{"$gt":70000000}},{"capital":1,"_id":0})))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Find the countries that have a population of over 100 million or less than a million</p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"$or":[{"population":{"$lt":1000000}},{"population":{"$gt":100000000}}]}, {"name":1, "_id":0})))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Find the names of countries beginning with "U" that are outside of Europe and North America</p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"$and":[{"name":{'$regex':"^U"}},{"continent":{"$nin":["Europe", "North America"]}}]},{"name":1,"_id":0})))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Find the names of all countries that contain a white space </p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"name":{"$regex":"^.*\s.*$"}},{"name":1,"_id":0})))
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Which country out of [China, Russia, United States] has the largest population</p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"name":{"$in":["China", "Russia", "United States"]}}).sort("population",-1).limit(1)))
</div>
</div>

<div class=q data-lang="py3">
Use [[Sort]] to find the last document in world
<p class=strong>Show the last document of world</p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find().sort("$natural", -1))[0])
</div>
</div>

<div class=q data-lang="py3">
<p class=strong>Show <code>capital</code> and <code>population</code> for the top 5 capital cities starting with the letter "M" that have a population of less than 3 million  </p>
<pre class=def>
</pre>
<div class=ans>
pp.pprint(list(db.world.find({"$and":[{"capital":{"$regex":"^M"}},{"population":{"$lt":3000000}}]}, {"_id":0, "capital":1, "population":1}).sort("population",-1).limit(5)))
</div>
</div>