Getting S3 objects' last modified datetimes with boto

If you’re using Django and django-storages, you can an unofficial API in the s3boto backend:

>>> from storages.backends.s3boto import _parse_datestring
>>> _parse_datestring("Fri, 20 Jul 2012 16:57:27 GMT")
datetime.datetime(2012, 7, 21, 2, 57, 27)

Unfortunately as of django-storages 1.1.5, this gives a naive datetime. You need to use django.utils.timezone to create an aware version:

>>> from django.utils import timezone
>>> naive = _parse_datestring("Fri, 20 Jul 2012 16:57:27 GMT")
>>> timezone.make_aware(naive, timezone.get_current_timezone())
datetime.datetime(2012, 7, 21, 2, 57, 27, tzinfo=<DstTzInfo 'Australia/Brisbane' EST+10:00:00 STD>) 

Convert the last_modified attribute to struct_time as given below

import time
for key in bucket.get_all_keys(): 
    time.strptime(key.last_modified[:19], "%Y-%m-%dT%H:%M:%S")

This will give a time.struct_time(tm_year, tm_mon, tm_mday, tm_hour, tm_min, tm_sec, tm_wday, tm_yday, tm_isdst) tuple for each key in the S3 bucket

this is working (tnx to jdennison from above):

after getting the key from s3:

import time
from time import mktime
from datetime import datetime

modified = time.strptime(key.last_modified, '%a, %d %b %Y %H:%M:%S %Z')

#convert to datetime
dt = datetime.fromtimestamp(mktime(modified))

Boto3 returns a datetime object for LastModified when you use the the (S3) Object python object:

https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/s3.html#S3.Object.last_modified

You shouldn’t need to perform any tortuous string manipulations.

To compare LastModified to today’s date (Python3):

import boto3
from datetime import datetime, timezone

today = datetime.now(timezone.utc)

s3 = boto3.client('s3', region_name='eu-west-1')

objects = s3.list_objects(Bucket='my_bucket')

for o in objects["Contents"]:
    if o["LastModified"] == today:
        print(o["Key"])

You just need to be aware that LastModifed is timezone aware, so any date you compare with it must also be timezone aware, hence:

datetime.now(timezone.utc)

This is for recent s3 list_objectsv2. The boto3 client gives lastModifed in datetime.datetime format, and ways to convert it is as below
links: boto3 link
and
aws s3 listobj

import datetime
from dateutil.tz import tzutc
# node s3 response '2019-06-17T18:42:57.000Z'
# python boto3 s3 response datetime.datetime(2019, 10, 1, 22, 41, 55, tzinfo=tzutc())
'''  {'ETag': '"c8ba0ad5003832f63690ea8ff9b66052"',
  'Key': 'SOMEFILE',
  'LastModified': datetime.datetime(2019, 10, 2, 18, 50, 47, tzinfo=tzutc()),
  'Size': 6390623,
  'StorageClass': 'STANDARD'}
'''
l = datetime.datetime(2019, 10, 1, 22, 41, 55, tzinfo=tzutc())
get_last_modified = int(l.strftime('%s'))
print(l)
print(get_last_modified) 

Using a Resource, you can get an iterator of all objects and then retrieve the last_modified attribute of an ObjectSummary.

import boto3

s3 = boto3.resource('s3')
bk = s3.Bucket(bucket_name)

[obj.last_modified for obj in bk.objects.all()][:10]

returns

[datetime.datetime(2020, 4, 17, 13, 23, 37, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 37, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 38, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 38, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 38, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 37, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 23, 37, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 17, 13, 20, 20, tzinfo=tzlocal()),
 datetime.datetime(2020, 4, 20, 8, 30, 2, tzinfo=tzlocal()),
 datetime.datetime(2020, 3, 26, 15, 33, 58, tzinfo=tzlocal())]

For just one s3 object you can use boto client’s head_object() method which is faster than list_objects_v2() for one object as less content is returned. The returned value is datetime similar to all boto responses and therefore easy to process.

head_object() method comes with other features around modification time of the object which can be leveraged without further calls after list_objects() result.

See this :
https://boto3.amazonaws.com/v1/documentation/api/latest/reference/services/s3.html#S3.Client.head_object

import boto3

s3 = boto3.client('s3')
response = client.head_object(Bucket, Key)
datetime_value = response["LastModified"]

import boto3
from boto3.session import Session

session = Session(aws_access_key_id=ACCESS_KEY, aws_secret_access_key=SECRET_KEY)
s3 = session.resource('s3')
my_bucket = s3.Bucket(BUCKET_NAME)

for obj in my_bucket.objects.all():
    print('{} | {}'.format(obj.key, obj.last_modified))

You can get last object last modified date like that:

With resource

boto3.resource('s3').Object(<BUCKET_NAME>, <file_path>).last_modified

With client

boto3.client('s3').head_object(<BUCKET_NAME>, <file_path>)['LastModified']

You can try sorting the returned list of objects by LastModified key

import boto3

s3_client = boto3.client('s3')
s3_response = s3_client.list_objects(Bucket=BUCKET_NAME)
sorted_contents = sorted(s3_response['Contents'], key=lambda d: d['LastModified'], reverse=True)
sorted_contents[0].get('Key')

You can remove reverse=True flag in order to get the earliest modified object. You can also sort by Size of the objects or any other properties you want.

Here is what I used for my lambda function…

Use s3.list_objects_v2(Bucket=Your_bucket_name) to list the objects then get the key LastModified from the contents.

import boto3
import json
import datetime  
   
s3 = boto3.client('s3')

def lambda_handler(event, context):
   bucket = Your-bucket-name
   try:
       listdata = s3.list_objects_v2(Bucket=bucket)
       contents = listdata['Contents'] if "Contents" in listdata else []
       for key in contents:
       lastmodified = str(key['LastModified'])
       print("lastmodified:", lastmodified)