如何将mongodb中的字符串日期转换为ISODate（）或DATE（），如果使用Python少于30天，如何将其删除？

Question

Using python I saved dates into MongoDB in below format,

completed_time : "2017:08:20 02:30:02"

Now I want to delete all entries which are older than 30 days. How can I implement that logic?

Answer 1

You can use the datetime module to convert your date/time string into a datetime object, and then convert it to an ordinal day (just a single number), and compare it to the day that was thirty days ago.

Hopefully this will do what you want:

import datetime

completed_time = "2017:07:20 02:30:02"

timeFormat = '%Y:%m:%d %H:%M:%S'
thisDate = datetime.datetime.strptime(completed_time, timeFormat).toordinal()

today = datetime.date.today()
thirtyDaysAgo = today.toordinal() - 30

if thisDate < thirtyDaysAgo:
    print("That needs deleting!")

Answer 2

You can do it more simply. This code is considerably longer than needed, in order to be explanatory.

I first create a collection of MongoDB records with dates that start from about a month and a half ago, and end about two two weeks ago.

>>> from pymongo import MongoClient
>>> client = MongoClient()
>>> db = client.test_database
>>> from datetime import datetime, timedelta
>>> some_dates = [datetime(2017, 7, d).strftime('%Y:%m:%d %H:%M:%S') for d in range(15,31)]+[datetime(2017, 8, d).strftime('%Y:%m:%d %H:%M:%S') for d in range(1,16)]
>>> posts = db.create_collection
>>> for some_date in some_dates:
...     post = {'completed_time': some_date, 'stuff': 'more stuff'}
...     post_id = posts.insert_one(post).inserted_id
... 

This calculates the time and date that is (or was) 30 days earlier than 'now' when I calculated it, and puts it in the format in you MongoDB database.

>>> boundary = (datetime.now()-timedelta(30)).strftime('%Y:%m:%d %H:%M:%S')

This counts the number of records in the database whose dates and times precede the value in boundary just calculated, for later reference.

>>> count = 0
>>> for post in posts.find({'completed_time': {'$lt': boundary}}):
...     count+=1
... 
>>> count
19

This is the one line that, with the calculation of boundary , does what you want.

>>> r = posts.delete_many({'completed_time': {'$lt': boundary}})

Now we can check that the correct number of records has been deleted.

>>> count = 0
>>> for post in posts.find({'completed_time': {'$lt': boundary}}):
...     count+=1
... 
>>> count
0