Introduction
In MongoDB, the limit() method is used to limit the number of documents returned in a query. The limit() method takes one argument, which is the maximum number of documents to return.
In this tutorial, we will learn how to use the limit() method in Python to limit the number of documents returned from a MongoDB database.
Prerequisites
To follow along with this tutorial, you will need:
- A MongoDB database
- The Python programming language installed on your computer
- The PyMongo driver for connecting to MongoDB from Python
Connecting to the MongoDB Database
To connect to a MongoDB database using PyMongo, we need to import the MongoClient class and then create an instance of that class.
Here’s an example:
from pymongo import MongoClient
# create a new MongoClient instance
client = MongoClient('mongodb://localhost:27017/')
In this example, we created a new MongoClient instance that will connect to a MongoDB server running on the localhost at the default port 27017.
If your MongoDB server is running on a different host or port, change the connection string accordingly.
Fetching Documents with limit()
To fetch documents from a MongoDB collection with a limit, we can use the limit() method.
Here’s an example:
# select a database
db = client['my_database']
# select a collection
collection = db['my_collection']
# find all documents and limit the result to 10
documents = collection.find().limit(10)
# print the documents
for doc in documents:
print(doc)
In this example, we fetched the first 10 documents from the “my_collection” collection using the limit() method. The find() method returns a cursor object, which we can use to iterate over the documents.
Sorting Documents Before Limiting
To sort the documents before limiting them, we can chain the sort() method to the cursor object.
Here’s an example:
# sort documents by the "name" field in descending order
documents = collection.find().sort("name", -1).limit(10)
# print the documents
for doc in documents:
print(doc)
In this example, we sorted the documents by the “name” field in descending order using the sort() method. We then limited the result to the first 10 documents using the limit() method.
Specifying a Starting Point with skip()
If we want to fetch documents starting from a specific point in the result set, we can use the skip() method along with the limit() method.
Here’s an example:
# skip the first 10 documents and limit the result to 10
documents = collection.find().skip(10).limit(10)
# print the documents
for doc in documents:
print(doc)
In this example, we skipped the first 10 documents using the skip() method and then limited the result to the next 10 documents using the limit() method.
Conclusion
In this tutorial, we learned how to use the limit() method in Python to limit the number of documents returned from a MongoDB database. We also learned how to sort documents before limiting and how to specify a starting point using the skip() method.
