Mongoengine creation_time attribute in Document

Question

I am trying to add a creation_time attribute to my documents. The following would be an example:

import datetime

class MyModel(mongoengine.Document):
    creation_date = mongo.DateTimeField()
    modified_date = mongo.DateTimeField(default=datetime.datetime.now)

Django models have built in parameter for their DateTimeField objects like add_now, etc., but MongoEngine does not support this.

I am wondering if best way to do this is the following:

m,created = MyModel.objects.get_or_create()
if created:
    m.creation_date = datetime.datetime.now()

or if there is a better, nicer way.

score 75 · Accepted Answer · answered Nov 15 '11 at 21:34

75

You could override the save method.

class MyModel(mongoengine.Document):
    creation_date = mongo.DateTimeField()
    modified_date = mongo.DateTimeField(default=datetime.datetime.now)

    def save(self, *args, **kwargs):
        if not self.creation_date:
            self.creation_date = datetime.datetime.now()
        self.modified_date = datetime.datetime.now()
        return super(MyModel, self).save(*args, **kwargs)

answered Nov 15 '11 at 21:34

Willian

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This is exactly what I needed. I had figured out the default bit, but overriding the save method to track the modified time is perfect. Thank you :) – Dawson Feb 04 '14 at 18:21
1

The problem with this though is that the save function won't be called if you do an update instead of a .save right? – Nazariy Jul 10 '15 at 02:16
override `clean` method instead of `save` should be better, [docs here](http://docs.mongoengine.org/guide/document-instances.html) – xialu Aug 07 '18 at 07:02
1

The modified_date can't be updated when I use the function `update` – DachuanZhao Mar 31 '19 at 13:45

score 28 · Answer 2 · edited Aug 07 '12 at 18:22

28

As an aside, the creation time is stamped into the _id attribute - if you do:

YourObject.id.generation_time

Will give you a datetime stamp.

edited Aug 07 '12 at 18:22

Mike Mackintosh

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answered Jul 17 '12 at 06:43

Ben Hughes

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4

This is better than the accepted answer. I've used `@property` on a function like this to get the created_time: `def created_at(self): return self.id.generation_time if self.id else None` – aaaronic Sep 12 '14 at 14:57

score 6 · Answer 3 · answered Jan 09 '13 at 21:49

One nice solution is reusing a single signal handler for multiple documents.

class User(Document):
    # other fields...
    created_at = DateTimeField(required=True, default=datetime.utcnow)
    updated_at = DateTimeField(required=True)

class Post(Document):
    # other fields...
    created_at = DateTimeField(required=True, default=datetime.utcnow)
    updated_at = DateTimeField(required=True)

def update_timestamp(sender, document, **kwargs):
    document.updated_at = datetime.utcnow()

signals.pre_save.connect(update_timestamp, sender=User)
signals.pre_save.connect(update_timestamp, sender=Post)

Be careful to assign a callable and not a fixed-value as the default, for example default=datetime.utcnow without (). Some of the other answers on this page are incorrect and would cause created_at for new documents to always be set to the time your app was first loaded.

It's also always better to store UTC dates (datetime.utcnow instead of datetime.now) in your database.

score 4 · Answer 4 · answered Aug 07 '12 at 18:19

# -*- coding: utf-8 -*-
from mongoengine import *
from mongoengine import signals
from datetime import datetime

class User(Document):
    email = StringField(required=True, unique=True)
    first_name = StringField(max_length=50)
    last_name = StringField(max_length=50)
    # audit fields
    created_on = DateTimeField(default=datetime.now())
    updated_on = DateTimeField(default=datetime.now())

    @classmethod
    def pre_save(cls, sender, document, **kwargs):
        document.updated_on = datetime.now()

signals.pre_save.connect(User.pre_save, sender=User)

Vikas Gulati · Answer 5 · 2016-03-18T11:14:28.770

If you are using the timestamp field in a bunch of Documents you can keep your code DRY by creating an abstract Document instead.

from datetime import datetime
from mongoengine import Document

class CreateUpdateDocument(Document):
    meta = {
        'abstract': True
    }

    # last updated timestamp
    updated_at = DateTimeField(default=datetime.now)

    # timestamp of when entry was created
    created_at = DateTimeField(default=datetime.now)

    def save(self, *args, **kwargs):
        if not self.created_at:
            self.created_at = datetime.now()
        self.updated_at = datetime.now()
        return super(CreateUpdateDocument, self).save(*args, **kwargs)

You might want to put `self.updated_at = datetime.now()` under an `else` statement, so you can keep the idea of "if the updated_at is none, that means the model was never updated". — ldavid, Jun 29 '15 at 13:19

score 4 · Answer 6 · answered Nov 07 '14 at 14:49

4

My preferred solution is to use the @property decorator to return the creation datetime as extracted from the ObjectId:

@property
def creation_stamp(self):
    return self.id.generation_time

answered Nov 07 '14 at 14:49

Emanuel Ey

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JohnDHH · Answer 7 · 2020-05-06T23:35:57.207

1

Try use lambda value:

import datetime
from mongoengine import Document

class MyModel(Document):
    creation_date = mongo.DateTimeField()
    modified_date = mongo.DateTimeField(default=lambda : datetime.datetime.now())

edited May 06 '20 at 23:35

answered Apr 23 '20 at 11:22

JohnDHH

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7

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No need to use a lambda, just use `mongo.DateTimeField(default=datetime.datetime.now)` – JanLikar Nov 30 '20 at 14:33

score 0 · Answer 8 · edited Aug 07 '12 at 18:23

0

Traditionally, I've set the creation_date default to datetime.now() and then have hidden the field on the admin form so you remove the possibility of a user overwriting the correct value. That requires almost no code.

Overriding the save method as suggested by Willian is also effective since you can programmtically block any updates to the creation_date and update the modfied_date at the same time.

edited Aug 07 '12 at 18:23

Mike Mackintosh

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answered Nov 18 '11 at 17:34

Darrell Hawley

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when you say "traditionally", do you mean using the Django ORM or MongoEngine specifically? – josephmisiti Nov 22 '11 at 17:25

score -8 · Answer 9 · answered Nov 18 '11 at 15:12

-8

You could use auto_now_add parameter as per documentation:

class MyModel(mongoengine.Document):
    creation_date = mongo.DateTimeField(auto_now_add = True)
    modified_date = mongo.DateTimeField(auto_now = True)

answered Nov 18 '11 at 15:12

Laur Ivan

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That is most unfortunate. Then overriding the save as in the accepted answer is the right answer. I'd create a patch to add the feature though :) – Laur Ivan Nov 23 '11 at 10:28

Mongoengine creation_time attribute in Document

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