PEP 559

pep-0559.rst

@@ -0,0 +1,78 @@
+PEP: 559
+Title: Built-in noop()
+Author: Barry Warsaw <barry@python.org>
+Status: Draft
+Type: Standards Track
+Content-Type: text/x-rst
+Created: 2017-09-08
+Python-Version: 3.7
+Post-History:
+
+
+Abstract
+========
+
+This PEP proposes adding a new built-in function called ``noop()`` which does
+nothing but return ``None``.
+
+
+Rationale
+=========
+
+It is trivial to implement a no-op function in Python.  It's so easy in fact
+that many people do it many times over and over again.  It would be useful in
+many cases to have a common built-in function that does nothing.
+
+One use case would be for PEP 553, where you could set the breakpoint
+environment variable to the following in order to effectively disable it::
+
+    $ setenv PYTHONBREAKPOINT=noop
+
+
+Implementation
+==============
+
+The Python equivalent of the ``noop()`` function is exactly::
+
+    def noop(*args, **kws):
+        return None
+
+The C built-in implementation is available as a pull request.
+
+
+Rejected alternatives
+=====================
+
+``noop()`` returns something
+----------------------------
+
+YAGNI.
+
+This is rejected because it complicates the semantics.  For example, if you
+always return both ``*args`` and ``**kws``, what do you return when none of
+those are given?  Returning a tuple of ``((), {})`` is kind of ugly, but
+provides consistency.  But you might also want to just return ``None`` since
+that's also conceptually what the function was passed.
+
+Or, what if you pass in exactly one positional argument, e.g. ``noop(7)``.  Do
+you return ``7`` or ``((7,), {})``?  And so on.
+
+The author claims that you won't ever need the return value of ``noop()`` so
+it will always return ``None``.
+
+
+Copyright
+=========
+
+This document has been placed in the public domain.
+
+
+
+..
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