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AWS S3 usage with Python & Boto3 library

Published at: 10/2/2020

Cloud based object storage has become an important part of any software application stack in recent times. AWS S3 has become the de-facto choice for this use case.

Use with python

The official sdk for python is Boto3 which provide API for using AWS S3.

Create boto3 configuration using AWS credentials

Below is an example of basic boto3 configuration. More details, options & best practices can be found in https://boto3.amazonaws.com/v1/documentation/api/latest/guide/configuration.html

import boto3

s3_resource = boto3.resource(
    "s3",
    aws_access_key_id="**********",
    aws_secret_access_key="**********",
)

S3 File download

Get file objects of a Bucket

Set bucket variable as name of the S3 bucket
Set prefix variable as name of S3 folder structure prefix. For eg. for file name like s3://bucketname/[clientid]/file1.csv, clientid can be used as prefix to get only files starting with a particular clientid.

Using the above, we can use the list_objects_v2 method to get a list of matching file objects

obj = s3_resource.meta.client.list_objects_v2(Bucket=bucket, Prefix=prefix)
all_keys_obj = obj['Contents']

The output of the above step is a list of s3 objects, like below

[
  {'Key': '*****', 'LastModified': datetime.datetime(2020, 3, 3, 12, 16, 16, tzinfo=tzutc()), 'ETag': '"*****"', 'Size': 869061, 'StorageClass': 'STANDARD', 'Owner': {'ID': '*****'}},
  ....
  {'Key': '*****', 'LastModified': datetime.datetime(2020, 3, 3, 12, 18, 10, tzinfo=tzutc()), 'ETag': '"*****"', 'Size': 23333915, 'StorageClass': 'STANDARD', 'Owner': {'ID': '*****'}}
]

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