Upload file to aws s3 with boto3

upload_s3_boto3.py

import mimetypes

def upload_s3(key, fileobj, bucket_name, cache=999999):
    """
    Lots of problems with new boto3 library. Many functions are not documented or wrongly documented
    1. s3.Object.metadata, s3.Object.cache_control, s3.Object.content_type: are read only, gotcha
    2. If you set it with `ExtraArgs={'Metadata':{...}}`, wrong again. Cache-Control will become amz-x-cache-control,
    not what you wanted
    3. If you set it with `ExtraArgs={'Cache-Control':'max-age=999'}`, wrong again! They need too be CacheControl and ContentType
    """
    s3 = boto3.resource('s3')
    obj = s3.Object(bucket_name, key)
    metadata = {'CacheControl': 'max-age=%i' % cache}
    metadata['ContentType'] = mimetypes.guess_type(key)[0]
    obj.upload_fileobj(fileobj, ExtraArgs=metadata)
    # This is how you allow the object to be read by public
    obj.Acl().put(ACL='public-read')
    return obj.content_length