When generating completions, bpython has to interact with the given objects. These objects might be the product of active development, so a bug in, for example, __getattribute__ of the user code happens sometimes. bpython should stomach such errors.

Minimal reproducing example:

$ bpython3
bpython version 0.17.1 on top of Python 3.7.3 /usr/bin/python3
>>> class BadClass:
...     def __getattribute__(self, name):
...         assert False, "Let's say there is a bug here."
... 
>>> x = BadClass()
>>> x(
Traceback (most recent call last):
  File "/usr/bin/bpython3", line 11, in <module>
    load_entry_point('bpython==0.17.1', 'console_scripts', 'bpython')()
  File "/usr/lib/python3/dist-packages/bpython/curtsies.py", line 191, in main
    exit_value = repl.mainloop(True, paste)
  File "/usr/lib/python3/dist-packages/bpython/curtsies.py", line 126, in mainloop
    self.process_event_and_paint(e)
  File "/usr/lib/python3/dist-packages/bpython/curtsies.py", line 90, in process_event_and_paint
    self.process_event(e)
  File "/usr/lib/python3/dist-packages/bpython/curtsiesfrontend/repl.py", line 603, in process_event
    return self.process_key_event(e)
  File "/usr/lib/python3/dist-packages/bpython/curtsiesfrontend/repl.py", line 757, in process_key_event
    self.add_normal_character(e)
  File "/usr/lib/python3/dist-packages/bpython/curtsiesfrontend/repl.py", line 1001, in add_normal_character
    self.cursor_offset += 1
  File "/usr/lib/python3/dist-packages/bpython/curtsiesfrontend/repl.py", line 1594, in _set_cursor_offset
    self.update_completion()
  File "/usr/lib/python3/dist-packages/bpython/curtsiesfrontend/repl.py", line 1032, in update_completion
    self.list_win_visible = self.complete(tab)
  File "/usr/lib/python3/dist-packages/bpython/repl.py", line 724, in complete
    self.set_docstring()
  File "/usr/lib/python3/dist-packages/bpython/repl.py", line 688, in set_docstring
    if not self.get_args():
  File "/usr/lib/python3/dist-packages/bpython/repl.py", line 635, in get_args
    if inspect.isclass(f):
  File "/usr/lib/python3.7/inspect.py", line 78, in isclass
    return isinstance(object, type)
  File "<bpython-input-5>", line 3, in __getattribute__
AssertionError: Let's say there is a bug here.
[$? = 1]

In the above session, I typed the (, but it did not appear on screen. (Boo me, I edited that part.)

I see two ways to fix this: Either wrap the code in complete in a try … finally, or wrap all the places where user code gets called. (This might be hard to find.)

None of the other issues seem to be related.