Datetime, MongoDB

Dates are essential in a database. A document may have a created, modified, or even deleted date—these timestamps can be queried with find().

In MongoDB we use the datetime Python module directly to encode and handle dates. We use "$lt" and "$gt" for range queries of dates.

Date time example

Please notice how we import parts of the datetime module with "import" statements at the top. We use relative dates here—based on the value of datetime.today().

from pymongo import MongoClient
from datetime import datetime
from datetime import timedelta

client = MongoClient("mongodb://127.0.0.1:27017")
db = client.blog

# Reset.
db.posts.delete_many({})

# Get today.
today = datetime.today()

# Insert some blog posts.
db.posts.insert_many([
    {"title": "Intro Post", "date": today - timedelta(days=200)},
    {"title": "Taking a Break", "date": today - timedelta(days=100)},
    {"title": "Goodbye Blog", "date": today},
])

# Find posts within last 150 days.
print("FIND :: RECENT POSTS")
cursor = db.posts.find({"date": {"$gt": today - timedelta(150)}})
for doc in cursor:
    print(doc)

# Find posts more than 180 days ago.
print("FIND :: OLDER POSTS")
cursor = db.posts.find({"date": {"$lt": today - timedelta(180)}})
for doc in cursor:
    print(doc)
FIND :: RECENT POSTS
{'date': datetime.datetime(2017, 7, 20, 12, 54, 13, 183000),
 'title': 'Taking a Break', '_id': ObjectId('59f4e065251497165850cd1f')}
{'date': datetime.datetime(2017, 10, 28, 12, 54, 13, 183000),
 'title': 'Goodbye Blog', '_id': ObjectId('59f4e065251497165850cd20')}
FIND :: OLDER POSTS
{'date': datetime.datetime(2017, 4, 11, 12, 54, 13, 183000),
 'title': 'Intro Post', '_id': ObjectId('59f4e065251497165850cd1e')}

Notes, find

Usually we want to find documents within a range of dates—either greater than, less than, or with both constraints. We can combine these queries into a single find call.

With datetime and timedelta, we can handle relative dates and times in Python. MongoDB can convert and handle dates created in this way.