pdb should try (hard) to avoid creating unnecessary exceptions, e.g. ``AttributeError`` when looking up commands, since this will show up in exception chains then (as "'Pdb' object has no attribute 'do_foo'").

See https://github.com/python/cpython/pull/4666 for an older PR in this regard.

My use case is to display the traceback for exceptions caused within/via Pdb.default(), to see more context when running code from pdb's prompt directly, where currently it would only display the exception itself.

Closing as the bug is not clear and the OP is not responding to requests on the PR to clarify it. Please create a new issue if you are still seeing a problem.

Given code like the following the try/except handling of Pdb (via `Cmd.onecmd`, see https://github.com/python/cpython/pull/4666) will mess with `sys.exc_info()`, which could be avoided:

```
try:
    raise ValueError()
except Exception as exc:
    e = exc
    __import__('pdb').set_trace()
```

```
% ./python t_issue36550.py
--Return--
> …/t_issue36550.py(5)<module>()->None
-> __import__('pdb').set_trace()
(Pdb) import sys; sys.exc_info()
(<class 'AttributeError'>, AttributeError("'Pdb' object has no attribute 'do_import'"), <traceback object at 0x7f92d2782500>)
```

The initial / better motivation was described in the original issue: with pdb++/pdbpp I want to display tracebacks/errors with errors that might occur via Pdb's prompt, where this then showed up as interfering with it.

(Sorry for not responding on https://github.com/python/cpython/pull/4666 earlier, but I think it is only part of this issue, and therefore it should not get closed, and also creating a new one instead does not sound useful to me, so please consider to re-open it instead.)

Reopened.

versions: - Python 3.6, Python 3.7, Python 3.8

nosy: + iritkatriel
messages: + msg401237

resolution: rejected
stage: patch review -> resolved