S3TempFile.py

import tempfile
import boto3
import sys


class S3TempFile(object):
    
    def __init__(self, bucket, key):
        self.bucket = bucket
        self.key = key
        self.tempfile = tempfile.TemporaryFile()
    
    def write(self, content):
        if sys.version_info[0] < 3:
            self.tempfile.write(content)
        else:
            self.tempfile.write(bytes(content,'utf-8'))
    
    def read(self):
        self.tempfile.seek(0)
        if sys.version_info[0] < 3:
            content = self.tempfile.read()
        else
            content = self.tempfile.read().decode()
        return content
    
    def get(self):
        return self.tempfile
    
    def download(self):
        s3_client = boto3.client('s3')
        s3_object = s3_client.get_object(Bucket=self.bucket, Key=self.key)
        content = s3_object['Body'].read()
        self.write(content.decode())

    def upload(self):
        s3_client = boto3.client('s3')
        self.tempfile.seek(0)
        s3_client.put_object(
            Body=self.tempfile,
            Bucket=self.bucket,
            Key=self.key)

    def close(self):
        self.tempfile.close()

# If the file is in the bucket
my_file = S3TempFile('my-bucket', 'key/destiny/file.txt')
my_file.download()
print(my_file.read())

# If you want to create the file in s3
my_file = S3TempFile('my-bucket', 'key/destiny/file.txt')
my_file.write('hello world!')
my_file.upload()

# At the end remember close the file, the GC will do for you, but it's a good practice
my_file.close()