FLASK + S3 Presigned URLs + FIle upload to s3

app.py

from s3 import AwsS3UploadClass
from config import id_key
from config import secret_key
from config import bucket_name
from flask import Flask
from flask import jsonify
from flask import request
import requests

app = Flask(__name__)


@app.route('/upload_file', methods=["POST"])
def upload_file():
  if request.method == "POST":
        file = None
        if "file" in request.files:
            file = request.files['file']
        else:
            return jsonify(error="requires file")
                # import s3 upload class

        s3 = AwsS3UploadClass(id_key,secret_key,bucket_name)
        # save file
        key = "file_name"
        file.save(key)
        # generate presgined post url
        response = s3.create_presigned_post(key)
        if response is None:
            return jsonify(error="key cannot None")

        files = [
            ('file', open(key, 'rb'))
        ]
        upload_response = requests.post(response['url'], data=response['fields'], files=files)

        if upload_response.status_code == 204:
            # remove file
            os.remove(key)
        return jsonify("file successfully uploaded to s3")
      
if __name__ == '__main__':
    app.run()

config.py

id_key="####"
secret_key="####"
bucket_name="####"

s3.py

import logging
import boto3
from botocore.exceptions import ClientError


class AwsS3UploadClass(object):

    def __init__(self, id_key, secret_key, bucket_name):
        """
        AWS s3 Upload Class

        Arguments:
            * id_key (string) aws access key id
            * secret_key (string) aws secret access key
            * bucket (string) the S3 bucket to connect to
        Attributes:
            * bucket (S3.Bucket) the bucket instance for the specified
              `bucket_name`
        """

        self.id_key = id_key
        self.secret_key = secret_key
        self.bucket_name = bucket_name

        self.client = boto3.client('s3',
                                   endpoint_url=None,
                                   aws_access_key_id=self.id_key,
                                   aws_secret_access_key=self.secret_key,
                                   region_name='eu-west-2'
                                   )


    def get_bucket(self, bucket_name):
        try:
            bucket = self.client.get_bucket(bucket_name)
        except ClientError as e:
            bucket = None
        return bucket

    def create_presigned_post(self, object_name,
                              fields=None, conditions=None, expiration=3600):
        """Generate a presigned URL S3 POST request to upload a file
        :param bucket_name: string
        :param object_name: string
        :param fields: Dictionary of prefilled form fields
        :param conditions: List of conditions to include in the policy
        :param expiration: Time in seconds for the presigned URL to remain valid
        :return: Dictionary with the following keys:
            url: URL to post to
            fields: Dictionary of form fields and values to submit with the POST
        :return: None if error.
        """
        s3_client = boto3.client('s3')
        try:
            response = s3_client.generate_presigned_post(self.bucket_name,
                                                         object_name,
                                                         Fields=fields,
                                                         Conditions=conditions,
                                                         ExpiresIn=expiration)
        except ClientError as e:
            logging.error(e)
            return None
        # The response contains the presigned URL and required fields
        return response