[Python-ideas] Use `isinstance` check during exception handling

[Random832]

Michael Selik <mike at selik.org> writes:
> After reading https://github.com/sjoerdjob/exhacktion/ I have a better
> understanding of what you want to accomplish. However, I'm still not
> clear on where the pain is coming from. If you find yourself writing
> an if in an except many times as you described:
>
> try:
>     os.chown("README.md", 100, 100)
> except EnvironmentError as e:
>     if e.errno == errno.ENOENT:
>         pass
>     else:
>         raise

You know, it occurs to me, there are some languages that support this as
a high-level feature. I.e. in Visual Basic

Try
    [Statements]
Catch ex As Exception When [Boolean-valued expression]
    [Statements]
End Try

This is in fact the *only* way that MS Windows "Structured Exception
Handling" exceptions work in C:

__try { ... }
__except([BOOL-valued expression]) { ... }

Both of these have the effect that the exception "was never caught" if
it returns false.