IPython raises AttributeError when sys.exit() is called within a try:except block

[davidrs06]

When running the following code in IPython (version 8.3.0 with python 3.9.7)

import sys
def test_exit():
    for i in range(2,-2,-1):
        try:
            print(1/i)
        except ZeroDivisionError:
            sys.exit("ERROR: tried to divide by zero, exiting script.")

test_exit()

I get the following output, which I guess is not expected

Output

0.5
1.0
---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
Input In [1], in test_exit()
      4 try:
----> 5     print(1/i)
      6 except ZeroDivisionError:

ZeroDivisionError: division by zero

During handling of the above exception, another exception occurred:

SystemExit                                Traceback (most recent call last)
    [... skipping hidden 1 frame]

Input In [1], in <cell line: 9>()
      7             sys.exit("ERROR: tried to divide by zero, exiting script.")
----> 9 test_exit()

Input In [1], in test_exit()
      6 except ZeroDivisionError:
----> 7     sys.exit("ERROR: tried to divide by zero, exiting script.")

SystemExit: ERROR: tried to divide by zero, exiting script.

During handling of the above exception, another exception occurred:

AssertionError                            Traceback (most recent call last)
    [... skipping hidden 1 frame]

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/interactiveshell.py:1982, in InteractiveShell.showtraceback(self, exc_tuple, filename, tb_offset, exception_only, running_compiled_code)
   1979 if exception_only:
   1980     stb = ['An exception has occurred, use %tb to see '
   1981            'the full traceback.\n']
-> 1982     stb.extend(self.InteractiveTB.get_exception_only(etype,
   1983                                                      value))
   1984 else:
   1985     try:
   1986         # Exception classes can customise their traceback - we
   1987         # use this in IPython.parallel for exceptions occurring
   1988         # in the engines. This should return a list of strings.

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:585, in ListTB.get_exception_only(self, etype, value)
    577 def get_exception_only(self, etype, value):
    578     """Only print the exception type and message, without a traceback.
    579 
    580     Parameters
   (...)
    583     value : exception value
    584     """
--> 585     return ListTB.structured_traceback(self, etype, value)

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:443, in ListTB.structured_traceback(self, etype, evalue, etb, tb_offset, context)
    440     chained_exc_ids.add(id(exception[1]))
    441     chained_exceptions_tb_offset = 0
    442     out_list = (
--> 443         self.structured_traceback(
    444             etype, evalue, (etb, chained_exc_ids),
    445             chained_exceptions_tb_offset, context)
    446         + chained_exception_message
    447         + out_list)
    449 return out_list

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:1118, in AutoFormattedTB.structured_traceback(self, etype, value, tb, tb_offset, number_of_lines_of_context)
   1116 else:
   1117     self.tb = tb
-> 1118 return FormattedTB.structured_traceback(
   1119     self, etype, value, tb, tb_offset, number_of_lines_of_context)

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:1012, in FormattedTB.structured_traceback(self, etype, value, tb, tb_offset, number_of_lines_of_context)
   1009 mode = self.mode
   1010 if mode in self.verbose_modes:
   1011     # Verbose modes need a full traceback
-> 1012     return VerboseTB.structured_traceback(
   1013         self, etype, value, tb, tb_offset, number_of_lines_of_context
   1014     )
   1015 elif mode == 'Minimal':
   1016     return ListTB.get_exception_only(self, etype, value)

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:865, in VerboseTB.structured_traceback(self, etype, evalue, etb, tb_offset, number_of_lines_of_context)
    856 def structured_traceback(
    857     self,
    858     etype: type,
   (...)
    862     number_of_lines_of_context: int = 5,
    863 ):
    864     """Return a nice text document describing the traceback."""
--> 865     formatted_exception = self.format_exception_as_a_whole(etype, evalue, etb, number_of_lines_of_context,
    866                                                            tb_offset)
    868     colors = self.Colors  # just a shorthand + quicker name lookup
    869     colorsnormal = colors.Normal  # used a lot

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:799, in VerboseTB.format_exception_as_a_whole(self, etype, evalue, etb, number_of_lines_of_context, tb_offset)
    796 assert isinstance(tb_offset, int)
    797 head = self.prepare_header(etype, self.long_header)
    798 records = (
--> 799     self.get_records(etb, number_of_lines_of_context, tb_offset) if etb else []
    800 )
    802 frames = []
    803 skipped = 0

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/IPython/core/ultratb.py:854, in VerboseTB.get_records(self, etb, number_of_lines_of_context, tb_offset)
    848     formatter = None
    849 options = stack_data.Options(
    850     before=before,
    851     after=after,
    852     pygments_formatter=formatter,
    853 )
--> 854 return list(stack_data.FrameInfo.stack_data(etb, options=options))[tb_offset:]

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/stack_data/core.py:546, in FrameInfo.stack_data(cls, frame_or_tb, options, collapse_repeated_frames)
    530 @classmethod
    531 def stack_data(
    532         cls,
   (...)
    536         collapse_repeated_frames: bool = True
    537 ) -> Iterator[Union['FrameInfo', RepeatedFrames]]:
    538     """
    539     An iterator of FrameInfo and RepeatedFrames objects representing
    540     a full traceback or stack. Similar consecutive frames are collapsed into RepeatedFrames
   (...)
    544     and optionally an Options object to configure.
    545     """
--> 546     stack = list(iter_stack(frame_or_tb))
    548     # Reverse the stack from a frame so that it's in the same order
    549     # as the order from a traceback, which is the order of a printed
    550     # traceback when read top to bottom (most recent call last)
    551     if is_frame(frame_or_tb):

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/stack_data/utils.py:98, in iter_stack(frame_or_tb)
     96 while frame_or_tb:
     97     yield frame_or_tb
---> 98     if is_frame(frame_or_tb):
     99         frame_or_tb = frame_or_tb.f_back
    100     else:

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/stack_data/utils.py:91, in is_frame(frame_or_tb)
     90 def is_frame(frame_or_tb: Union[FrameType, TracebackType]) -> bool:
---> 91     assert_(isinstance(frame_or_tb, (types.FrameType, types.TracebackType)))
     92     return isinstance(frame_or_tb, (types.FrameType,))

File ~/Software/anaconda3/envs/code_testing/lib/python3.9/site-packages/stack_data/utils.py:172, in assert_(condition, error)
    170 if isinstance(error, str):
    171     error = AssertionError(error)
--> 172 raise error

AssertionError: 

Would anyone know what is the issue and how it could be solved ? I'm expecting this script to print the error message when i reaches 0, and simply interrupting the execution. I do get what I want if I use the following code instead:

import sys
def test_exit():
    for i in range(2,-2,-1):
        if i == 0:
            sys.exit("ERROR: tried to divide by zero, exiting script.")
        else:
            print(1/i)

test_exit()

Thanks in advance !

[davidrs06]

Actually the issue might be related to the argument given to sys.exit(). I get a TypeError: object of type 'NoneType' has no len()if I call sys.exit() or sys.exit(1). However, the following code, which assigns the ZeroDivisionError to a variable to be printed inside the exceptblock works:

import sys
def test_exit():
    for i in range(2,-2,-1):
        try:
            print(1/i)
        except ZeroDivisionError as msg:
            sys.exit(msg)

test_exit()

Output:

0.5
1.0
An exception has occurred, use %tb to see the full traceback.

SystemExit: division by zero

/home/david/Software/anaconda3/lib/python3.9/site-packages/IPython/core/interactiveshell.py:3452: UserWarning: To exit: use 'exit', 'quit', or Ctrl-D.
  warn("To exit: use 'exit', 'quit', or Ctrl-D.", stacklevel=1)

However, if I convert the msg variable to a string to append more information, things don't work anymore:

import sys
def test_exit():
    for i in range(2,-2,-1):
        try:
            print(1/i)
        except ZeroDivisionError as msg:
            sys.exit(str(msg)+'. Script stopped because of ZeroDivisionError. Please check your code to avoid zero division.')

test_exit()    

Is this something expected ? I could just print the complementary information before calling sys.exit(msg), but you might want to explore this in more detail if it turns out to be a a real issue.