On Sun, Dec 18, 2022 at 07:38:06PM -0500, David Mertz, Ph.D. wrote:
However, if you want to allow these types to possibly *do* something with the strings inside (validate them, canonicalize them, do a security check, etc), I think I like the other way:
#2
class html(str): pass class css(str): pass
The problem with this is that the builtins are positively hostile to subclassing. The issue is demonstrated with this toy example: class mystr(str): def method(self): return 1234 s = mystr("hello") print(s.method()) # This is fine. print(s.upper().method()) # This is not. To be useable, we have to override every string method that returns a string. Including dunders. So your class becomes full of tedious boiler plate: def upper(self): return type(self)(super().upper()) def lower(self): return type(self)(super().lower()) def casefold(self): return type(self)(super().casefold()) # Plus another 29 or so methods This is not just tedious and error-prone, but it is inefficient: calling super returns a regular string, which then has to be copied as a subclassed string and the original garbage collected. -- Steve