How can I disable Django's csrf protection only in certain cases?

I'm trying to write a site in Django where the API URLs are the same as user-facing URLs. But I'm having trouble with pages which use POST requests and CSRF protection. For example, if I have a page /foo/add I want to be able to send POST requests to it in two ways:

1. As an end user (authenticated using a session cookie) submitting a form. This requires CSRF protection.
2. As an API client (authenticated using a HTTP request header). This will fail if CSRF protection is enabled.

I have found various ways of disabling CSRF, such as @csrf_exempt, but these all disable it for the entire view. Is there any way of enabling/disabling it at a more fine-grained level? Or am I just going to have to implement by own CSRF protection from scratch?

There is a section of Django's CSRF Protection documentation titled View needs protection for one path which describes a solution. The idea is to use @csrf_exempt on the whole view, but when the API client header is not present or invalid, then call a function annotated with @csrf_protect.