[Python-checkins] r82008 - in python/branches/py3k: Doc/library/doctest.rst

[r.david.murray]

Author: r.david.murray
Date: Wed Jun 16 01:46:40 2010
New Revision: 82008

Log:
Merged revisions 81634 via svnmerge from 
svn+ssh://pythondev@svn.python.org/python/trunk

........
  r81634 | r.david.murray | 2010-05-31 21:42:41 -0400 (Mon, 31 May 2010) | 2 lines
  
  #7583: clarify discussion of hard tab expansion in doctests.
........


Modified:
   python/branches/py3k/   (props changed)
   python/branches/py3k/Doc/library/doctest.rst

Modified: python/branches/py3k/Doc/library/doctest.rst
==============================================================================
--- python/branches/py3k/Doc/library/doctest.rst	(original)
+++ python/branches/py3k/Doc/library/doctest.rst	Wed Jun 16 01:46:40 2010
@@ -282,11 +282,8 @@
 How are Docstring Examples Recognized?
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-In most cases a copy-and-paste of an interactive console session works fine, but
-doctest isn't trying to do an exact emulation of any specific Python shell.  All
-hard tab characters are expanded to spaces, using 8-column tab stops.  If you
-don't believe tabs should mean that, too bad:  don't use hard tabs, or write
-your own :class:`DocTestParser` class.
+In most cases a copy-and-paste of an interactive console session works fine,
+but doctest isn't trying to do an exact emulation of any specific Python shell.
 
 ::
 
@@ -317,6 +314,21 @@
   blank line, put ``<BLANKLINE>`` in your doctest example each place a blank line
   is expected.
 
+* All hard tab characters are expanded to spaces, using 8-column tab stops.
+  Tabs in output generated by the tested code are not modified.  Because any
+  hard tabs in the sample output *are* expanded, this means that if the code
+  output includes hard tabs, the only way the doctest can pass is if the
+  :const:`NORMALIZE_WHITESPACE` option or directive is in effect.
+  Alternatively, the test can be rewritten to capture the output and compare it
+  to an expected value as part of the test.  This handling of tabs in the
+  source was arrived at through trial and error, and has proven to be the least
+  error prone way of handling them.  It is possible to use a different
+  algorithm for handling tabs by writing a custom :class:`DocTestParser` class.
+
+  .. versionchanged:: 2.4
+     Expanding tabs to spaces is new; previous versions tried to preserve hard tabs,
+     with confusing results.
+
 * Output to stdout is captured, but not output to stderr (exception tracebacks
   are captured via a different means).
 
@@ -1778,4 +1790,3 @@
 .. [#] Examples containing both expected output and an exception are not supported.
    Trying to guess where one ends and the other begins is too error-prone, and that
    also makes for a confusing test.
-