How can I stop Python from deleting a name binding, when that name is used for binding the exception that is caught? When did this change in behaviour come into Python?
I am writing code to run on both Python 2 and Python 3:
exc = None
try:
1/0
text_template = "All fine!"
except ZeroDivisionError as exc:
text_template = "Got exception: {exc.__class__.__name__}"
print(text_template.format(exc=exc))
Notice that exc is explicitly bound before the exception handling, so Python knows it is a name in the outer scope.
On Python 2.7, this runs fine and the exc name survives to be used in
the format call::
Got exception: ZeroDivisionError
Great, this is exactly what I want: The except clause binds the name
and I can use that name in the rest of the function to refer to the
exception object.
On Python 3.5, the format call fails because apparently the exc
binding is deleted::
Traceback (most recent call last):
File "<stdin>", line 8, in <module>
NameError: name 'exc' is not defined
Why is the exc binding deleted from the outer scope? How are we meant
to reliably preserve the name binding to use it after the except
clause?
When did this change come into Python, where is it documented?
Would I be right to report this as a bug in Python 3?