Updating or replacing MongoDB documents using Python and PyMongo

Overview:

One or more documents present in a MongoDB collection can be modified using the following methods of PyMongo:
- collection.update_one()
- collection.update_many()
- collection.replace_one()
In the filter condition for the update methods, a specific operator can be provided based on the type of the field and the kind of operation applied on the field.

Updating multiple MongoDB documents:

The Python example program below, uses collection.update_many()method to update any number of documents in a MongoDB collection, that matches a specified filter criteria.
In this example, in all the documents of a MongoDB collection named orders, where the value for the field avenue matches the string “NASDAQGS”, those values are modified to “NYSE”.

Example:

# import MongoClient from pymongo
from pymongo import MongoClient

# Create a MongoDB client
mongoDBConnection = MongoClient('localhost', 27017)

# Get a collection instance
collection = mongoDBConnection.sample.orders

# Update the venue in the order documents
updateResult = collection.update_many({'Venue': "NasdaqGS"}, {'$set': {'Venue': "NYSE"}})

# Print the updated document count
print("Number of documents updated on the MongoDB collection:")
print(updateResult.deleted_count)

Output:

Number of documents updated on the MongoDB collection:

Replacing the whole Document of a MongoDB collection:

A specific document in a collection can be replaceds with another document by specifying a filter condition.

Example:

# import MongoClient from pymongo

from pymongo import MongoClient

# Create a MongoDB client

mongoDBConnection = MongoClient('localhost', 27017)

# Get a collection instance

collection = mongoDBConnection.sample.exhibits

# Print the collection before replacing a document

print("Contents of a MongoDB document collection before replacing an erroneous document:")

for doc in collection.find():

print(doc)

# Replace a document who has several corrections at field level and value level

updateResult = collection.replace_one({"title": "Encyclopedia of everything under the universe"},

{

"title": "Encyclopedia of everything under the universe",

"author":"Authors",

"authorcount":25000,

"type": "DVD",

"isbn": "xxx-x-xx-xxxxxx-m"

}

)

# Print the collection after replacing an erroneous document

print("Contents of a MongoDB document collection after replacing an erroneous document:")

for doc in collection.find():

print(doc)

Output:

Contents of a MongoDB document collection before replacing an erroneous document:

{'_id': ObjectId('5aba7fe074d9af6fff2f2219'), 'title': 'Encyclopedia of everything under the universe', 'author': 'Author Name', 'type': 'Book', 'isbn': 'xxx-x-xx-xxxxxx-a'}

{'_id': ObjectId('5aba802174d9af6fff2f221a'), 'title': 'Unwritten book', 'author': 'Author Name', 'type': 'Book', 'isbn': 'xxx-x-xx-xxxxxx-b'}

Contents of a MongoDB document collection after replacing an erroneous document:

{'_id': ObjectId('5aba7fe074d9af6fff2f2219'), 'title': 'Encyclopedia of everything under the universe', 'author': 'Authors', 'authorcount': 25000, 'type': 'DVD', 'isbn': 'xxx-x-xx-xxxxxx-m'}

{'_id': ObjectId('5aba802174d9af6fff2f221a'), 'title': 'Unwritten book', 'author': 'Author Name', 'type': 'Book', 'isbn': 'xxx-x-xx-xxxxxx-b'}