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Yes, raising an exception with a result as a payload is one option. Other option is to check a result. Something like:
def _compile_is_valid(value):
 p, loc = value
 return loc is None or loc == _locale.setlocale(_locale.LC_CTYPE)
def _compile_cache_if(value):
 p, loc = value
 return loc is not False
@lru_cache(_MAXCACHE, is_valid=_compile_is_valid, cache_if=_compile_cache_if)
def _compile1(pattern, flags):
 # internal: compile pattern
 if isinstance(pattern, _pattern_type):
 if flags:
 raise ValueError(
 "cannot process flags argument with a compiled pattern")
 return pattern, False
 if not sre_compile.isstring(pattern):
 raise TypeError("first argument must be string or compiled pattern")
 p = sre_compile.compile(pattern, flags)
 if flags & DEBUG:
 return p, False
 if not (p.flags & LOCALE):
 return p, None
 if not _locale:
 return p, False
 return p, _locale.setlocale(_locale.LC_CTYPE)
def _compile(pattern, flags):
 p, loc = _compile1(pattern, flags)
 return p