'de facto', without '-'. See for instance https://www.merriam-webster.com/dictionary/defacto

Thank you! Changed.

Better, but without having used argparse yet, I think something like "Use ' ' as the scheme value to get the default scheme in urlsplit and urlparse." might be even better.

I settled for this. # We use '' as the scheme value for default scheme in urlsplit and urlparse.

Uses_relative only seems to affect “urljoin”, not “urlsplit” nor “urlparse”. The empty string means that you can join one relative URL onto another one.

The comment applies to all three lists, uses_relative, uses_netloc and uses_params.
All of them have '' (empty string) listed as supported scheme, because that is the default
def urlsplit(url, scheme='', allow_fragments=True):
and
def urlparse(url, scheme='', allow_fragments=True):

And the current comment is:
# A classification of schemes ('' means apply by default)

• I think, the existing comment is confusing, and thus, this change is to make it a bit clear.

Ah, I misunderstood the comment. I thought you were listing the functions that the lists affected. What about something like

The empty string classifies relative URLs with no scheme specified, being the default returned by “urlsplit” and “urlparse”

Sounds good to me. I will write it as "default value".

The empty string classifies relative URLs with no scheme specified, being the default value returned by “urlsplit” and “urlparse”

Modified the comment as per our discussion here.