COMP4332/RMBI4310
Using NoSQL in Python
Prepared by Raymond Wong
NoSQL in Python
Presented by Raymond Wong
1
PyMongo


We can use MongoDB in Python
(when we are running the MongoDB
server).
We should install the package
“PyMongo” (i.e., “pymongo”) in Python
NoSQL in Python
2
Including Package

At the beginning of the “Python” script,
include the following package.
Python
from pymongo import MongoClient
NoSQL in Python
3
Database Connection

Inside the “Python” script, include the
following.
Python
Get the database connection
client = MongoClient("mongodb://localhost:27017")
…
client.close()
NoSQL in Python
Perform some MongoDB operations
Close the database connection
4
Database Connection

For each Python operation related to
MongoDB, it is better to include the
following to handle exceptions related to
MongoDB
Python
try:
…
Some operations in Python (including the previous operations just
shown and the operations to be shown later)
except pymongo.errors.ConnectionFailure as error:
print(error)
SQL
5
Database Connection

In summary, one simple implementation can be:
Python
try:
client = MongoClient("mongodb://localhost:27017")
…
client.close()
except pymongo.errors.ConnectionFailure as error:
print(error)
SQL in Python
6
Database Connection


Alternatively, you could use “try…
except” for each individual NoSQLrelated operation (rather than a whole
block of all NoSQL-related operations)
In the following, we just focus on
NoSQL-related operations. Thus, the
operations handling exceptions will not
be shown in the following slides.
SQL
7
Specifying Database

Before we perform the MongoDB
operation, we need to select the
database as follows.
Python
Getting a database named “university”
db = client["university"]
…
NoSQL in Python
8
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
9
1. Creating Collection


In MongoDB, there is no need to create
a collection explicitly (e.g.,
db.createCollection("student")).
When we insert the first document into
a collection, the collection will be
created automatically.
NoSQL in Python
10
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
11
2. Inserting Documents
Python
Similar to what we have seen in MongoDB
db.student.insert(
{
"sid": "12345678",
"sname": "Raymond",
"byear": 1998
}
)
Remember to have the double-quotation on LHS (i.e., the field name)
NoSQL in Python
12
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
13
3. Updating Documents
Python
Similar to what we have seen in MongoDB
db.student.update_many({"sid": "12345678"}, {"$set":{"byear":2008}})
Here, we use “update_many” instead of “update”
Remember to have the double-quotation on each internal operation
(e.g., “$set”)
NoSQL in Python
14
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
15
4. Querying Documents (find)
Similar to what we have seen in MongoDB
Python
listOfStudent = db.student.find({"byear":1998})
for oneStudent in listOfStudent:
tempSid = oneStudent["sid"]
tempSname = oneStudent["sname"]
tempByear = oneStudent["byear"]
We could get the field value by specifying with “[…]”
NoSQL in Python
16
4. Querying Documents
(aggregate)
Similar to what we have seen in MongoDB
Python
listOfStudent = db.student.aggregate([{"$match": {"byear": 1998}}])
for oneStudent in listOfStudent:
tempSid = oneStudent["sid"]
tempSname = oneStudent["sname"]
tempByear = oneStudent["byear"]
We could get the field value by specifying with “[…]”
NoSQL in Python
17
4. Querying Documents
(distinct)
Similar to what we have seen in MongoDB
Python
listOfStudent = db.student.distinct("sname", {"byear":1998})
for oneStudent in listOfStudent:
tempSname = oneStudent
NoSQL in Python
It returns a list of strings (for “sname”)
18
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
19
5. Removing Documents
Similar to what we have seen in MongoDB
Python
db.student.remove({"byear":1998})
NoSQL in Python
20
MongoDB Operation
1.
2.
3.
4.
5.
6.
Creating Collection
Inserting Documents
Updating Documents
Querying Documents
Removing Documents
Dropping Collection
NoSQL in Python
21
6. Dropping Collection
Similar to what we have seen in MongoDB
Python
db.student.drop()
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22