How can I determine the site prefix of a SharePoint site via an API?

Question

I use the SharePoint API to access a tenant SharePoint with a SharePoint REST API call that looks like {site_prefix}/_api/web/GetFileByServerRelativeUrl({path})/... where site_prefix is usually something like /sites/siteName but I think that it can sometimes also be /teams/siteName. Given a webUrl of a driveItem, I was using a regular expression like re.match(r"/sites/([^/]+)", webUrlPath).group() and this usually works because most sites prefixes start with /sites/.

However, I've run into a tenant that does not have a prefix like this, but rather their own custom prefix, so their item's webUrl looks like https://contoso.sharepoint.com/customname/. I would like to know how to determine that the site prefix here is customname so that I can plug it into the SharePoint REST API call that I mentioned in the beginning. I assume that this has something to do with "Managed Paths", but I do not know how to find the managed paths programmatically. If necessary, I also have access to the Graph API.

I have considered just trying /sites/([^/]+), /teams/([^/]+), and as last resort ([^/]+), but I think this may not always work because (please correct if I'm wrong) the prefix may also have multiple slashes making it hard to know where the prefix ends and path begins.

Answer 1

It was simpler than I initially thought once I realized that I can get the siteUrl from any given drive item. I'm using the graph API to get the SharepointIds with ?$select=sharepointids followed by parsing out the path with urllib.parse.urlparse(result["sharepointIds"]["siteUrl"]).path (Python). This is working so far, as I get /sites/name for most sites and /customname on the problem site.