[Python-Dev] PEP 553: Built-in debug() (original) (raw)

Giampaolo Rodola' g.rodola at gmail.com
Tue Sep 5 22:31:59 EDT 2017

It's a lot to type (27 characters).

True. Personally I have a shortcut in my IDE (Sublime) so I when I type "pdb" -> TAB it auto completes it.

Python linters (e.g. flake8 [1]) complain about this line because it contains two statements. Breaking the idiom up into two lines further complicates the use of the debugger,

I see this more as an advantage. After all a pdb line is "temporary" and you never want to commit it. When you do it is by accident so you want it to be more noticeable. I can configure my IDE to use flake8 and highlight the pdb line for me so that I can immediately see it because it's not PEP-8 compliant. I can have a GIT commit hook which checks there's no "pdb.set_trace()" in the files I'm committing: https://github.com/giampaolo/psutil/blob/master/.git-pre-commit#L93-L96 Somehow I think debug() would make this a bit harder as it's more likely a "debug()" line will pass unnoticed. For this reason I would give a -1 to this proposal.

It ties debugging directly to the choice of pdb. There might be other debugging options, say if you're using an IDE or some other development environment.

Personally I would find it helpful if there was a hook to choose the default debugger to use on "pdb.set_trace()" via .pdbrc or PYTHONDEBUGGER environment variable or something. I tried (unsuccessfully) to run ipdb on "pdb.set_trace()", I gave up and ended up emulating auto completion and commands history with this: https://github.com/giampaolo/sysconf/blob/master/home/.pdbrc.py

On Wed, Sep 6, 2017 at 9:14 AM, Barry Warsaw <barry at python.org> wrote:

I’ve written a PEP proposing the addition of a new built-in function called debug(). Adding this to your code would invoke a debugger through the hook function sys.debughook().

Like the existing sys.displayhook() and sys.excepthook(), you can change sys.debughook() to point to the debugger of your choice. By default it invokes pdb.settrace(). With this PEP instead of: foo() import pdb; pdb.settrace() bar() you can write: foo() debug() bar() and you would drop into the debugger after foo() but before bar(). More rationale and details are provided in the PEP: https://www.python.org/dev/peps/pep-0553/ Unlike David, but like Larry, I have a prototype implementation: https://github.com/python/cpython/pull/3355 Cheers, -Barry P.S. This came to me in a nightmare on Sunday night, and the more I explored the idea the more it frightened me. I know exactly what I was dreaming about and the only way to make it all go away was to write this thing up.

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