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Don't use numeric references.

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Barry Warsaw 2017-09-13 16:54:22 -07:00
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pep-0553.rst
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@ -39,7 +39,7 @@ enter the debugger. However this idiom has several disadvantages.
debugging options, say if you're using an IDE or some other development debugging options, say if you're using an IDE or some other development
environment. environment.
* Python linters (e.g. flake8 [1]_) complain about this line because it * Python linters (e.g. flake8 [linters]_) complain about this line because it
contains two statements. Breaking the idiom up into two lines further contains two statements. Breaking the idiom up into two lines further
complicates the use of the debugger, complicates the use of the debugger,
@ -50,7 +50,7 @@ other languages, and utilizing a convention that already exists in Python.
Proposal Proposal
======== ========
The JavaScript language provides a ``debugger`` statement [2]_ which enters The JavaScript language provides a ``debugger`` statement [java]_ which enters
the debugger at the point where the statement appears. the debugger at the point where the statement appears.
This PEP proposes a new built-in function called ``breakpoint()`` This PEP proposes a new built-in function called ``breakpoint()``
@ -70,7 +70,7 @@ and it can be set to a different function to change the debugger that
default value of ``sys.breakpointhook()`` to make it easy to reset. default value of ``sys.breakpointhook()`` to make it easy to reset.
This exactly models the existing ``sys.displayhook()`` / This exactly models the existing ``sys.displayhook()`` /
``sys.__displayhook__`` and ``sys.excepthook()`` / ``sys.__displayhook__`` and ``sys.excepthook()`` /
``sys.__excepthook__`` hooks [3]_. ``sys.__excepthook__`` [hooks]_.
The signature of the built-in is ``breakpoint(*args, **kws)``. The positional The signature of the built-in is ``breakpoint(*args, **kws)``. The positional
and keyword arguments are passed straight through to ``sys.breakpointhook()`` and keyword arguments are passed straight through to ``sys.breakpointhook()``
@ -100,7 +100,7 @@ can have various values:
value may be a string with no dots, in which case it names a built-in value may be a string with no dots, in which case it names a built-in
callable, e.g. ``PYTHONBREAKPOINT=int``. (Guido has expressed the callable, e.g. ``PYTHONBREAKPOINT=int``. (Guido has expressed the
preference for normal Python dotted-paths, not setuptools-style entry point preference for normal Python dotted-paths, not setuptools-style entry point
syntax [4]_ .) syntax [syntax]_.)
This environment variable allows external processes to control how breakpoints This environment variable allows external processes to control how breakpoints
are handled. Some uses cases include: are handled. Some uses cases include:
@ -147,7 +147,7 @@ Evaluation of $PYTHONBREAKPOINT
There has been some mailing list discussion around this topic. The basic There has been some mailing list discussion around this topic. The basic
behavior as described above does not appear to be controversial. Guido has behavior as described above does not appear to be controversial. Guido has
expressed a preference for ``$PYTHONBREAKPOINT`` consultation happening in expressed a preference for ``$PYTHONBREAKPOINT`` consultation happening in
the default implementation of ``sys.breakpointhook``. the default implementation of ``sys.breakpointhook`` [envar]_.
The one point of discussion relates to whether the value of The one point of discussion relates to whether the value of
``$PYTHONBREAKPOINT`` should be loaded on interpreter start, and whether its ``$PYTHONBREAKPOINT`` should be loaded on interpreter start, and whether its
@ -157,11 +157,11 @@ It is the PEP author's opinion that the environment variable need only be
looked up at the time of use. It is also the author's opinion that the value looked up at the time of use. It is also the author's opinion that the value
of the environment variable can be accessed each time ``sys.breakpointhook`` of the environment variable can be accessed each time ``sys.breakpointhook``
is run, to allow for maximum functional flexibility. Because this feature is run, to allow for maximum functional flexibility. Because this feature
enters the debugger, any performance improvements for caching is negligible enters the debugger, any performance improvements for caching will be
and does not outweigh the flexibility. Further, because the special case of negligible and do not outweigh the flexibility. Further, because the special
``PYTHONBREAKPOINT=0`` is fast-tracked, the no-op code path is quite fast, and case of ``PYTHONBREAKPOINT=0`` is fast-tracked, the no-op code path is quite
should be in the noise given the function calls of ``breakpoint()`` -> fast, and should be in the noise given the function calls of ``breakpoint()``
``sys.breakpointhook()``. -> ``sys.breakpointhook()``.
Breakpoint bytecode Breakpoint bytecode
@ -191,7 +191,7 @@ it as handy as ``breakpoint.pm()``.
Implementation Implementation
============== ==============
A pull request exists with the proposed implementation [5]_. A pull request exists with the proposed implementation [impl]_.
Rejected alternatives Rejected alternatives
@ -243,15 +243,23 @@ Version History
References References
========== ==========
.. [1] http://flake8.readthedocs.io/en/latest/ .. [linters]
http://flake8.readthedocs.io/en/latest/
.. [2] https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/debugger .. [java]
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/debugger
.. [3] https://docs.python.org/3/library/sys.html#sys.displayhook .. [hooks]
https://docs.python.org/3/library/sys.html#sys.displayhook
.. [4] http://setuptools.readthedocs.io/en/latest/setuptools.html?highlight=console#automatic-script-creation .. [syntax]
http://setuptools.readthedocs.io/en/latest/setuptools.html?highlight=console#automatic-script-creation
.. [5] https://github.com/python/cpython/pull/3355 .. [impl]
https://github.com/python/cpython/pull/3355
.. [envar]
https://mail.python.org/pipermail/python-dev/2017-September/149447.html
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