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find one Example (MongoDB)Invoke the MongoDB find_one method to find a single matching document. Test against None.
Python
Find_one, MongoDB. Often just a single match is needed in a MongoDB query. The find_one method is ideal here. It returns the values found, or None if nothing matches.
With None, we can test the database to ensure a document is not present. This helps us avoid conflicts. Find_one is easy to use once the MongoDB is ready.
An example. Consider this example program. We reset the "categories" collection in a "content" database. We add 3 documents, each with a language key.
And We set the status one each document as well. This can be retrieved from the result of find_one.
Detail We invoke find_one on the categories collection. One match for "Java" is returned.
from pymongo import MongoClient client = MongoClient("mongodb://127.0.0.1:27017") db = client.content # Reset. db.categories.delete_many({}) # Insert some documents. db.categories.insert_many([ {"language": "C#", "status": 1}, {"language": "Java", "status": 1}, {"language": "Python", "status": 2}, ]) # Find a matching document. print("FIND ONE JAVA") result = db.categories.find_one({"language": "Java"}) print(result) # Access the status key. print("STATUS") print(result["status"]) # This query matches no documents. print("FIND ONE FORTRAN") result = db.categories.find_one({"language": "Fortran"}) print(result) if result == None: print("NOT FOUND")
FIND ONE JAVA {'status': 1, 'language': 'Java', '_id': ObjectId('59efce1a25149714a00cf82d')} STATUS 1 FIND ONE FORTRAN None NOT FOUND
Notes, None. Our database does not include an entry matching "Fortran." So the None value is returned. We can test None directly in Python.
None
A summary. With the return value of find_one, we can access individual keys and values (like in a Python dictionary). The syntax of MongoDB here is clear.
Dictionary
C#VB.NETPythonGolangJavaSwiftRust
Dot Net Perls is a collection of tested code examples. Pages are continually updated to stay current, with code correctness a top priority.
Sam Allen is passionate about computer languages. In the past, his work has been recommended by Apple and Microsoft and he has studied computers at a selective university in the United States.
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