try:
    if_nametoindex('qweqweq')
except Exception as err:
    print(err.errno)

None

I think it's a bug because I can not distinguish from any other OS errors precisely (like EPERM vs ENOENT or so)

Linked PRs

• gh-100218: correctly set errno when socket.if_{nametoindex,indextoname} raise OSError #140905
• [3.14] gh-100218: correctly set errno when socket.if_{nametoindex,indextoname} raise OSError (GH-140905) #141284
• [3.13] gh-100218: correctly set errno when socket.if_{nametoindex,indextoname} raise OSError (GH-140905) #141285