mentalisttraceur / python-exceptioncontext

Context Managers for Controlling Exception Chaining

Provides a different way of controlling exception chaining (the implicit __context__ and explicit __cause__) beyond just raise ... from ....

Versioning

This library's version numbers follow the SemVer 2.0.0 specification.

Installation

pip install exceptioncontext

Usage

Import as needed:

from exceptioncontext import cause, context, suppress_context

Explicitly chain exception (set __cause__):

with cause(Exception("foo")):
    raise Exception("bar")

Override implicitly chained exception (set __context__):

with context(Exception("foo")):
    raise Exception("bar")

Manually control context suppression (set __suppress_context__):

with suppress_context(False):
    raise Exception("foo")

exceptioncontext makes exception chaining fully independent of the raise statement, and freely composable with other code:

with cause(earlier_exception):
    helper_function()

Portability

Portable to all releases of both Python 3 and Python 2.

(The oldest tested is 2.5, but it will likely work as far back as 2.2 when paired with something like with-as-a-function_.)

On implementations of Python where setting the exception chaining attributes on an exception raises an AttributeError, exceptioncontext gracefully degrades to doing nothing.