GeezerVison is showing github.com — Cannot define global variables in .pdbrc · Issue #119580 · python/cpython
Cannot define global variables in .pdbrc #119580DescriptionBug report
Bug description:
#116660 closed gh-90095 to properly handle commands issued through -c or .pdbrc. The pdb documentation also speaks of convenience variables which is a debugging global variable. I was expecting to be able to define a variable starting with $ as defined in the documentation below, and make manipulations to that variable through commands in a .pdbrc, but doing the following $_capture_list = [] in .pdbrc issues a syntax error
To set a temporary global variable, use a convenience variable. A convenience variable is a variable whose name starts with $. For example, $foo = 1 sets a global variable $foo which you can use in the debugger session. The convenience variables are cleared when the program resumes execution so it’s less likely to interfere with your program compared to using normal variables like foo = 1.
CPython versions tested on:
3.11
Operating systems tested on:
Linux
Linked PRs
ActivityDelengowski commented on May 26, 2024 ContributorAuthor More actions I may be misunderstanding the paragraph. Perhaps the convenience variable is restricted to the scope of the command and should not be persistent throughout the entire debugging session.
Example program
from itertools import product
x_axis = range(6)
y_axis = range(6)
for x,y in product(x_axis, y_axis):
...In the same directory .pdbrc
$equal_components = []
b 7, (x ==y)
commands
$equal_components.append((x,y))
print($equal_components)
continue
Displays *** SyntaxError: invalid syntax
Instead I attempt
b 7, (x ==y)
commands
$equal_components.append((x,y))
print($equal_components)
continue
Then invoke with python -m pdb example.py and manually type
(Pdb) commands
(com) $equal_components = []
(com) end
(Pdb) continue
Which does not work either, I'm presuming because there is no breakpoint to associate that command with.
What does work is
b 7, (x ==y)
commands
print((x,y))
continue
Breakpoint 1 at /tmp/example_pdbrc.py:7
(Pdb) c
(0, 0)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
(1, 1)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
(2, 2)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
(3, 3)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
(4, 4)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
(5, 5)
> /tmp/example_pdbrc.py(7)<module>()
-> ...
The program finished and will be restarted
gaogaotiantian commented on May 26, 2024 First of all, you listed that you were using Python 3.11, is that the case? Convenience variable is a feature added in Python 3.12 so it won't work with 3.11. Delengowski commented on May 26, 2024 ContributorAuthor More actions
First of all, you listed that you were using Python 3.11, is that the case? Convenience variable is a feature added in Python 3.12 so it won't work with 3.11.
Ah, let me try 3.12 with your backport Delengowski commented on May 26, 2024 ContributorAuthor More actions Defining a convenience variable through .pdbrc does indeed work correctly when using 3.12 with your backport. Although from the paragraph I believe I was misunderstanding how it persists between breakpoints (it doesn't appear to).
With that being said I do find it unclear that convenience variables were added in 3.12 or specific convenience variables ($_frame, etc.) were added in 3.12, or really what of the previous 6 paragraphs was added 3.12. gaogaotiantian commented on May 26, 2024 I agree that the added version is not super clear and I can try to improve it. However, about the persistence:
The convenience variables are cleared when the program resumes execution
Your program resumes execution between breakpoints so the convenience variables will be cleared. I think this behavior is well-described. Delengowski commented on May 26, 2024 ContributorAuthor More actions Yes I misunderstood the behavior of the convenience variables. As such I will close this.
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