Python thinks program.py arg is a python.exe arg

Python Help
1
  • I’m new to Python 3.14. I’m used to using Python 3.11.9.
  • Python 3.14 is on Windows 2025 Datacenter v24H2. Windows 2025 is also new to me. The .venv is activated.
  • I’m using Windows Terminal to do run the got.bat file.

I’m running a program using a batch file called got.bat, in debug mode. This is the only line in the got.bat file: .venv\scripts\python -m pdb ptool.py -tablescsv. I would like to start the pdb debugger for the program pacetool.py.

But I get this error when running got.

usage: python.exe -m pdb [-h] [-c command] (-m module | -p pid | pyfile) [args ...]
python.exe -m pdb: error: argument -p/--pid: invalid int value: 'acetablescsv'

Python thinks -tablegscsv is a argument to the python.exe when it’s an argument to my program pacetool.py.

Is there any way to fix this? Other programs I have been working with today on this same machine, same installation of python work fine.

What I tried

  • python -m pdb ptool.py -tablescsv
  • python -m pdb ptool.py -v Showing version info actually works for my program.

but I still get the same error.

I also tried this in got.bat: python -m pdb test.py -tablescsv and get the same error. test.py contains:

print("Hello world")
print(f"sys.argv={sys.argv}")

Did I find a bug? Python is only processing the first letter of my program argument “-tablescsv”. It should process the whole argument.

Thank you.

EDIT: When I do python -h there is no -p or -pid option listed.

2

You’re right. This seems to be a bug introduced when pdb switched from using getopt to argparse in 3.13.

3

A solution is to use -- to make it clear that all following arguments are not options:

python -m pdb -- test.py -pacetablescsv
4
  • Should I file a bug report? How do I do that?
  • Would the bug be for pdb?

Is there someone able to confirm this is a bug in Python 3.14? Maybe the bug has been filed already. I have never filed a bug before.

5

When I do python -m pdb -- test.py -tablescsv I get the same error above.

These work fine (without pdb):

  • python test.py
  • python test.py -myarg

Possibly the same bug

6

Possible workaround: Add a double hyphen after the script name. This should terminate option parsing and pass the rest on to your script. Note that your script will then see the "--" argument in sys.argv, so it’ll need to ignore that.

rosuav@sikorsky:~$ python3.15 -m pdb test.py -p
usage: python3.15 -m pdb [-h] [-c command] (-m module | -p pid | pyfile) [args ...]
python3.15 -m pdb: error: argument -p/--pid: expected one argument
rosuav@sikorsky:~$ python3.15 -m pdb test.py -- -p
> /home/rosuav/test.py(1)<module>()
-> import sys
(Pdb) r
['test.py', '--', '-p']
--Return--
> /home/rosuav/test.py(2)<module>()->None
-> print(sys.argv)
(Pdb) q

Note that using a single hyphen with multiple letters is often interpreted as either a series of separate flags (eg ls -lat is equivalent to ls -l -a -t), or as a flag with a parameter (eg git commit -mHello is equivalent to --message Hello), and a number of tools and libraries will assume that one or other of these is true. The normal way to write a longer parameter name is with a double hyphen. So another workaround would be to change your script to accept --pacetablegscsv, which pdb won’t expect and will therefore pass on to your script, rather than interpreting -p as an option and acetablegscsv as its parameter.

1 Like
7

Thank you. I will look into this.

This issue still seems like a bug to me (similar bug reports in a previous post) as when -m pdb is used, the command line processor should look at all parameters after test.py as going to the program test.py.

8

It does seem so; what I suggested is a workaround, a way to have the script work correctly in spite of the oddity.

9

And it gets more weird. This is another program on the same Python 3.14 machine that works with single dash long options.

python -m pdb piecework.py -daily -test -adminemailonly

The only difference is the program above uses more than on option and no options begin with “-p”. So there still seems to be a special case where pdb doesn’t work right.

10

See above for the explanation of single-hyphen options. PDB recognizes four such options: -h, -c, -m, and -p. If your word starts with one of those, it will be interpreted accordingly.

What you have here is a conflict of interpretation. Yes, it’s only a conflict because of a bug, but to understand the behaviour, you have to understand the conflict that’s happening :slight_smile:

I do recommend sticking to the common convention of using a double hyphen for word options, though. It’ll make a lot of things easier.