Description

assignee = None
closed_at = None
created_at = <Date 2020-12-01.15:13:18.533>
labels = ['type-feature', 'library', '3.9', '3.10', '3.11']
title = '[doc] pdb access to return value'
updated_at = <Date 2021-08-05.08:10:47.486>
user = 'https://github.com/romuald'

activity = <Date 2021-08-05.08:10:47.486>
actor = 'Romuald'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-12-01.15:13:18.533>
creator = 'Romuald'
dependencies = []
files = []
hgrepos = []
issue_num = 42524
keywords = ['patch']
message_count = 5.0
messages = ['382259', '398853', '398855', '398894', '398896']
nosy_count = 2.0
nosy_names = ['Romuald', 'iritkatriel']
pr_nums = ['23601', '27612']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42524'
versions = ['Python 3.9', 'Python 3.10', 'Python 3.11']

Activity

1. romuald commented on Dec 1, 2020

   

   romualdmannequin

   on Dec 1, 2020

   MannequinAuthor

   More actions

   When using the pdb module, there is currently no way to easy access the current return value of the stack

   This return value is accessed by the 'retval command'

   I propose using the currently unused argument to allow storing the return value in the local variables, accessible via the debugger

   For example:

       def foo():
           debugger()
           return ComplexObject()
   
       def bar():
           return foo()

   (pdb) retval
   <ComplexObject instance at 0x1234>
   (pdb) retval zz
   (pdb) zz.attribute
   'some value'
2. romuald

   added

   3.10 (EOL)end of lifeend of life

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   type-featureA feature request or enhancementA feature request or enhancement

   on Dec 1, 2020
3. iritkatriel commented on Aug 3, 2021

   

   iritkatriel

   on Aug 3, 2021

   Member

   More actions

   It actually is in the locals, and it's called __return__. So you can access it with

   locals()['__return__']

   I'll try to see where that can be documented.
4. iritkatriel

   added

   3.9 (EOL)end of lifeend of life

   3.11only security fixesonly security fixes

   on Aug 3, 2021
5. iritkatriel

   changed the title [-]pdb access to return value[/-] [+][doc] pdb access to return value[/+] on Aug 3, 2021
6. iritkatriel

   added

   3.9 (EOL)end of lifeend of life

   3.11only security fixesonly security fixes

   on Aug 3, 2021
7. iritkatriel

   changed the title [-]pdb access to return value[/-] [+][doc] pdb access to return value[/+] on Aug 3, 2021
8. iritkatriel commented on Aug 3, 2021

   

   iritkatriel

   on Aug 3, 2021

   Member

   More actions

   I just noticed your PR. Would you like to continue working on this?

   I think we should update the documentation of retval (in the doc and in the function's doctring) to say:

   """
   retval
   Print the return value for the last return of a function. Alternatively, the return value can be accessed with locals()['__return__'].
   """

   Then add unit tests and examples as you did.
9. romuald commented on Aug 4, 2021

   

   romualdmannequin

   on Aug 4, 2021

   MannequinAuthor

   More actions

   I'm not sure I follow.

   You wish to "simply" update the doc? (and not update the retval to allow storing it into a varible. I'm OK with that)

   But if we choose this, I'm not sure what needs changing in the doctests :-?

   Another interrogation: is the use locals() really necessary? I can see that I can simply use __return__ to access the return object.
   Is there a reason to access it via locals() inside pdb?
10. iritkatriel commented on Aug 4, 2021

    

    iritkatriel

    on Aug 4, 2021

    Member

    More actions

    Yes, exactly - to update the doc so that the next person who needs it will easily find a way to do it (which was not available to you when you created this issue).

    The test should assert that what the doc says, so that if someone breaks documented functionality we will immediately know.

    Your point about accessing __return__ directly from the prompt is interesting - sure, if that works just document that and make sure the test fails if we make a change that breaks it.
11. ezio-melotti

    transferred this issue fromon Apr 10, 2022
12. gaogaotiantian commented on Oct 7, 2023

    

    gaogaotiantian

    on Oct 7, 2023

    Member

    More actions

    The return value can be accessed with $_retval now.
13. gaogaotiantian

    closed this as completedon Oct 7, 2023

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