New submission from Sean Reifschneider <[EMAIL PROTECTED]>:
I'm giving a Python tutorial to a bunch of local people and have decided
to use the Python.org tutorial to go by. One of the things I found I
wanted in the section on the "pass" statement was more information about
it's use. But I also think it's worth mentioning using the
NotImplementedError if pass is used for stubbing out code.
This patch to the tutorial includes some example use cases, and also a
reference to NotImplementedError. I would appreciate some review
however, as I'm not sure this discussion is appropriate.
Included below is the patch, for ease of reading, but it's also attached as
a patch (taken against trunk today).
Sean
===========
Index: Doc/tutorial/controlflow.rst
===================================================================
--- Doc/tutorial/controlflow.rst (revision 67072)
+++ Doc/tutorial/controlflow.rst (working copy)
@@ -166,7 +166,36 @@
... pass # Busy-wait for keyboard interrupt (Ctrl+C)
...
+This is commonly used for creating minimal classes like with exceptions, or
+for skipping unwanted exceptions::
+ >>> class ParserError(Exception):
+ ... pass
+ ...
+ >>> try:
+ ... import audioop
+ ... except ImportError:
+ ... pass
+ ...
+
+Another place it can be used is as a place-holder for a function or
+conditional body when you are working on new code, allowing you to keep
+thinking at a more abstract level. However, as :keyword:`pass` is silently
+ignored, a better choice may be to raise a :exc:`NotImplementedError`
+exception::
+
+ >>> def initlog(*args):
+ ... raise NotImplementedError # Open logfile if not already open
+ ... if not logfp:
+ ... raise NotImplementedError # Set up dummy log back-end
+ ... raise NotImplementedError # Call log initialization handler
+ ...
+
+If :keyword:`pass` were used here and you later ran tests, they may fail
+without indicating why. Using :exc:`NotImplementedError` causes this code
+to raise an exception, allowing you to tell exactly where code that you
+need to complete is.
+
.. _tut-functions:
Defining Functions
----------
assignee: fdrake
components: Documentation
files: pass-examples.patch
keywords: easy, needs review, patch, patch
messages: 75452
nosy: fdrake, jafo
priority: normal
severity: normal
status: open
title: Docs: Provide some examples of "pass" use in the tutorial.
type: feature request
versions: Python 2.7
Added file: http://bugs.python.org/file11926/pass-examples.patch
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<http://bugs.python.org/issue4247>
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