How do I set the Content-Type of an existing S3 key with boto3?

Question

I want to update the Content-Type of an existing object in a S3 bucket, using boto3, but how do I do that, without having to re-upload the file?

    file_object = s3.Object(bucket_name, key)
    print file_object.content_type
    # binary/octet-stream
    file_object.content_type = 'application/pdf'
    # AttributeError: can't set attribute

Is there a method for this I have missed in boto3?

Related questions:

• How to set Content-Type on upload
• How to set the content type of an S3 object via the SDK?

Answer 1

In addition to @leo's answer, be careful if you have custom metadata on your object. To avoid side effects, I propose adding Metadata=object.metadata in the leo's code otherwise you could lose previous custom metadata:

s3 = boto3.resource("s3")
object = s3.Object(bucket_name, key)
object.copy_from(
          CopySource={'Bucket': bucket_name, 'Key': key},
          Metadata=object.metadata,
          MetadataDirective="REPLACE",
          ContentType="application/pdf"
)