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

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:
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

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:

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.set_trace().
> With this PEP instead of:
>     foo()
>     import pdb; pdb.set_trace()
>     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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Giampaolo - http://grodola.blogspot.com
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