Retrieving Etag of an s3 object using boto3 client

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There is a scenario where I need to verify the checksum(md5) of a file stored in s3 bucket. This can be achieved when uploading the file by specifying the checksum value in the metadata of api call. But in my case, I wanted to verify the checksum after put the data into bucket programmatically. Every object in S3 will have attribute called 'ETag' which is the md5 checksum calculated by S3.

Is there anyway to get the ETag of a specific object and compare the checksum of both local file & file stored in s3 using boto3 client in a python script?

Do not use the ETag of an object in a bucket to determine object equivalence for an object in another bucket (with the same key). In some experiments, I found for large objects the ETag is not consistent from region to region. For example, a large file in a bucket in us-east-1 may have a different ETag when it is copied to us-east-2. The consistency of the ETag value from bucket to bucket varies from object to object. I saw where some large objects do have the same ETag in both regions. I resorted to creating my own tags with the md5sum in it and when I copy an object from one bucket to another, I also copy the tags.

S3, ETag (string) -- import boto3 s3 = boto3.resource('s3') copy_source = { 'Bucket': 'mybucket', 'Key': 'mykey' } s3.meta.client.copy(copy_source, The name of the bucket from which an analytics configuration is retrieved. For S3 buckets, if versioning is enabled, users can preserve, retrieve, and restore every version of the object stored in the bucket. In this article, we will understand how to enable versioning for a bucket and retrieve all versions of an object from AWS web interface as well as Python boto library.

Boto3 api has provided a way to get the metadata of an object stored in s3. The following snippet will help to get the metadata via programmatically :

>>> s3_cli = boto3.client('s3')
>>> s3_resp = s3_cli.head_object(Bucket='ventests3', Key='config/ctl.json')
>>> print pprint.pprint(s3_resp)
>>> pp.pprint(s3_resp)
{u'AcceptRanges': 'bytes',
 u'ContentLength': 4325,
 u'ContentType': 'binary/octet-stream',
 u'ETag': '"040c003386f1e2001816d32f2125d07a"',
 u'LastModified': datetime.datetime(2018, 9, 20, 7, 15, 3, tzinfo=tzutc()),
 u'Metadata': {},
 'ResponseMetadata': {'HTTPHeaders': {'accept-ranges': 'bytes',
                                      'content-length': '4325',
                                      'content-type': 'binary/octet-stream',
                                      'date': 'Thu, 20 Sep 2018 07:20:53 GMT',
                                      'etag': '"040c003386f1e2001816d32f2125d07a"',
                                      'last-modified': 'Thu, 20 Sep 2018 07:15:03 GMT',
                                      'server': 'AmazonS3',
                                      'x-amz-id-2': 'P2wapOciWCKPfol2sBgoo11tRdr4KwKcDJ/nHW7LZn00mvKfMYyfAPPV2tIcf3Vu+lrV57NBARY=',
                                      'x-amz-request-id': '42AF970E7C9AA18C'},
                      'HTTPStatusCode': 200,
                      'HostId': 'P2wapOciWCKPfol2sBgoo11tRdr4KwKcDJ/nHW7LZn00mvKfMYyfAPPV2tIcf3Vu+lrV57NBARY=',
                      'RequestId': '42AF970E7C9AA18C',
                      'RetryAttempts': 0}}

>>> s3obj_etag = s3_resp.['ETag'].strip('"')
>>> print s3obj_etag
'040c003386f1e2001816d32f2125d07a'

The head_object() method in s3 client object will fetch the metadata (headers) of a given object stored in the s3 bucket.

Check the Integrity of an Object Uploaded to Amazon S3, Follow these steps to verify the integrity of the uploaded object using the MD5 checksum value: Note: The entity tag (ETag) is a hash of the  When copying an object, you can request that Amazon S3 encrypt the target object by using either the AWS managed encryption keys or by using your own encryption key. You can do this regardless of the form of server-side encryption that was used to encrypt the source, or even if the source object was not encrypted.

Actually, the above code will generate error as if there is a missing parameter.

This works for me

s3.meta.client.head_bucket(Bucket='mybucket')

GetObject - Amazon Simple Storage Service, Retrieves objects from Amazon S3. If you encrypt an object by using server-​side encryption with customer-provided encryption keys (SSE-C) when you store​  The same happens with data.put('hello') which is the method recommended by the top answers at How to write a file or data to an S3 object using boto3 and with data.put_object: 'dict' object has no attribute 'put_object'.

Using Python, Storing and retrieving data Python support is provided through the Boto 3 library. cos = boto3.resource('s3', endpoint_url=endpoint) for bucket in Raw output from 'list_buckets()' in apiary: { u'Contents': [ { u'ETag':  Here are some common things you might want to do with your S3 objects that Boto3 can help with: Listing objects in your buckets. Downloading objects directly from a bucket. Changing bucket object permissions. Setting a bucket policy on a bucket. Uploading files to a bucket. Deleting files from a bucket.

S3, This is the same name as the method name on the client. ETag (string) -- The Server-side encryption algorithm used when storing this object in S3 (e.g., AES256, Name of the bucket for which the accelerate configuration is retrieved. Note: The response of list_objects() is truncated to 1000 objects. Use the markers in the response to retrieve the remainder of objects in the bucket. Appreciate your response. I attempted s3client.download_file(Bucket, Key, Filename) but encountered an error: AttributeError: 'S3' object has no attribute 'download’.

Boto 3 Documentation, import boto3 # Let's use Amazon S3 s3 = boto3.resource('s3'). Now that you have an Retrieve waiter instance that will wait till a specified # S3 bucket exists ETag (string) -- The current version of the origin access identity created. Retrieves objects from Amazon S3. To use GET , you must have READ access to the object. If you grant READ access to the anonymous user, you can return the object without using an authorization header.