Example to write a file to an S3 bucket:

from io import BytesIO
import boto3

aws_access_key_id = "your_aws_access_key_id"
aws_secret_access_key = "your_aws_secret_access_key"
region_name = "your_aws_region_name"
aws_bucket_name = "my-bucket-name"

s3_client = boto3.client(
  's3',
  aws_access_key_id = aws_access_key_id,
  aws_secret_access_key= aws_secret_access_key,
  region_name = region_name
) 

s3_client.upload_fileobj(BytesIO(file_contents), aws_bucket_name, file_name)