This package was available under exc on PyPI and has undergone a recent
migration to meta_exc. It will no longer be available to be installed via
pip install exc after 2019-06-17. Please update your codebase to use
pip install meta_exc.
The meta_exc package provides a metaclass for exceptions, allowing
on-the-spot subclassing, e.g. in order to have one exception class per
raise site. It is easy to use, as the following example illustrates
import meta_exc
class FruitError(meta_exc.Exception):
pass
import sys
fruit = sys.argv[1]
try:
if fruit in ('lemon', 'lime', 'grapefruit'):
raise FruitError['too_sour']('%ss are too sour!' % fruit)
elif fruit == 'jalapeno':
raise FruitError['too_spicy']('%ss are too spicy!' % fruit)
print("Nom nom")
except FruitError['too_sour']:
print('I did not eat the fruit because it was too sour...')
except FruitError:
print('I did not eat the fruit for some reason.')
There are wrapped versions of all the builtins: meta_exc.TypeError,
meta_exc.IOError and so forth. The metaclass is called
DerivableException.
The intended usage of meta_exc is for each exception site to raise an
exception with a unique class, so that they may be caught
individually.
meta_exc.Exception['a/b'] == meta_exc.Exception.specialize('a/b') == meta_exc.Exception.specialize('a').specialize('b')
meta_exc should work with Python >= 2.6 and Python >= 3. It does not
work in Python 2.4 because of limitations on exception types. In
Python 3, try/except does not consult instancehook or subclasshook, so
meta_exc.Exception cannot be used to catch plain Exception (but it
can be in Python 2).