Devin Jeanpierre wrote:
Inheriting from SyntaxError doesn't work! When I create a new exception, I
generally subclass from the built-in exception it most resembles, in case
there was some reason to also catch it via an ancestor. But I'm not sure if
that is really all that useful an idea in practice. How do you folk do it?
If somebody wanted to catch a ValueError, would they also mean to
catch my error? (The same with SyntaxError and so on). Probably not.
If your error represents a value error, then yes they would.
But in that case, why should I subclass ValueError instead of just using
ValueError itself? Writing my own exceptions is only useful if I intend to
give the caller the *choice* of either treating my exception the same or
different from ValueError: that is, if my error is a more specific kind of
ValueError. If it is not a specific kind of value error, then just use the
generic built-in ValueError exception instead.
try:
x = some_function()
except MyValueError:
# treat my errors specially
except ValueError:
# any other kind of ValueError caught here
vs.
try:
x = some_function()
except ValueError:
# any kind of ValueError caught here, including MyValueError
The same goes for all exception types, although in practice I find that I
generally only subclass ValueError.
--
Steven
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