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.

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.

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.