Common methods and examples of PymonGo querying documents

PymonGo is an official driver that interacts with MongoDB in Python.It provides a set of rich methods for querying and operating documents in MongoDB.This article will introduce the common methods of querying documents in PymonGo and provide relevant examples. First, we need to install Pymon and configure the MongoDB connection.You can use the following commands to install pymongo: pip install pymongo Before starting to write code, make sure you have created databases and sets on local or remote MongoDB servers. Next, we will view some commonly used query methods and examples: 1. Query all documents: from pymongo import MongoClient # O client = MongoClient("mongodb://localhost:27017/") # Get the database and collection db = client["mydatabase"] collection = db["mycollection"] # Query all documents result = collection.find() for doc in result: print(doc) In this example, we checked all the documents in the set through the `Find ()` method, and print each document with the `For` cycle. 2. Inquiry documents according to the condition: # Query document with age greater than 30 result = collection.find({"age": {"$gt": 30}}) # Query name is John's documentation result = collection.find({"name": "John"}) # J The name starts with the document starting with J result = collection.find({"name": {"$regex": "^J"}}) In these examples, we use different conditions to query documents.`$ gt` is greater than,` $ regex` indicates a regular expression matching. 3. Query the document of the specified field: # 字 field field result = collection.find({}, {"name": 1}) # Just query the name and age field result = collection.find({}, {"name": 1, "age": 1}) By specifying the fields that need to be returned in the second parameter, we can limit the field of the inquiries of the Chinese document. 4. Query sorting and restriction results: # Sort according to the sequence of age result = collection.find().sort("age", 1) # Sort according to age order, and limit the results to 2 documents result = collection.find().sort("age", -1).limit(2) Use the `sort ()` method to sort the query results.Parameter `1` represents the order,` -1` represents the order.`limit ()` method can limit the number of results documents. The above example shows the commonly used query method in Pymon.According to your specific needs, you can combine and use these methods to query the document.Remember to modify the connection string and collection name according to your mongodb configuration. Finally, attach a complete example code: from pymongo import MongoClient # O client = MongoClient("mongodb://localhost:27017/") # Get the database and collection db = client["mydatabase"] collection = db["mycollection"] # Query all documents result = collection.find() for doc in result: print(doc) # Close connection client.close() I hope this article can help you master the common methods of querying documents in PymonGo and play a role in actual projects.If necessary, you can check the official Pymon document to get more details.