On 12.04.20 02:20, Soni L. wrote:
I figured something better instead. you can have a class ESpace, but
you use it like so:
espace = ESpace()
try:
foo(espace=espace)
except espace.module.submodule.Exception:
...
e.g. for builtins:
espace = ESpace()
try:
raise espace.ValueError
except espace.ValueError:
...
and it dynamically creates subclasses of whatever you give it. I'm not
sure how doable this is in current python, but it's super close to
what I want. so hey if it works well, we can promote it to the stdlib?
just need to encourage ppl not to check the type of their espace
argument so you can silently swap the external one for the stdlib one
and nothing breaks.
(still need a better way to pass it into operators but eh)
This is possible for example by defining ESpace as a class which returns
the corresponding exception subclasses via `__getattr__` and stores them
in a cache. In order to work with a default (i.e. if no espace is
provided) some base class which delegates attribute lookups directly to
`builtins` would be required. Something like the following should do:
import builtins
import inspect
class BaseESpace:
def __getattr__(self, name):
obj = getattr(builtins, name, None)
if inspect.isclass(obj) and issubclass(obj, Exception):
return obj
else:
raise AttributeError(name)
class ESpace(BaseESpace):
def __init__(self):
self.cache = {}
def __getattr__(self, name):
try:
return self.cache[name]
except KeyError:
custom = type(name, (super().__getattr__(name),), {})
self.cache[name] = custom
return custom
def func_works(espace=BaseESpace()):
raise espace.ValueError('foo')
def func_bug(espace=BaseESpace()):
int('xyz')
espace = ESpace()
try:
func_works(espace=espace)
except espace.ValueError:
print('custom exception raised')
except ValueError:
print('builtin exception raised')
try:
func_works()
except espace.ValueError:
print('custom exception raised')
except ValueError:
print('builtin exception raised')
try:
func_bug()
except espace.ValueError:
print('custom exception raised')
except ValueError:
print('builtin exception raised')
So it seems there are plenty of options to realize this in custom
projects without a change to the syntax. In any way, these approaches
require the API developers to add the extra `espace` parameter to their
functions, so all of this can only work based on mutual agreement.
Regarding operators, you can always `try / except` and then re-raise a
similar exception from `espace`.
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