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Merged revisions 67117-67119,67123-67124,67143 via svnmerge from

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  r67117 | georg.brandl | 2008-11-06 11:17:58 +0100 (Thu, 06 Nov 2008) | 2 lines

  #4268: Use correct module for two toplevel functions.
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  r67118 | georg.brandl | 2008-11-06 11:19:11 +0100 (Thu, 06 Nov 2008) | 2 lines

  #4267: small fixes in sqlite3 docs.
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  r67119 | georg.brandl | 2008-11-06 11:20:49 +0100 (Thu, 06 Nov 2008) | 2 lines

  #4245: move Thread section to the top.
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  r67123 | georg.brandl | 2008-11-06 19:49:15 +0100 (Thu, 06 Nov 2008) | 2 lines

  #4247: add "pass" examples to tutorial.
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  r67124 | andrew.kuchling | 2008-11-06 20:23:02 +0100 (Thu, 06 Nov 2008) | 1 line

  Fix grammar error; reword two paragraphs
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  r67143 | georg.brandl | 2008-11-07 09:27:39 +0100 (Fri, 07 Nov 2008) | 2 lines

  Fix syntax.
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This commit is contained in:
Georg Brandl 2008-11-07 09:39:56 +00:00
parent 6570d071fa
commit a971c65f1d
5 changed files with 202 additions and 165 deletions
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35
Doc/tutorial/controlflow.rst
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@ -196,6 +196,41 @@ required syntactically but the program requires no action. For example::
... pass # Busy-wait for keyboard interrupt (Ctrl+C)
...
This is commonly used for creating minimal classes such as exceptions, or
for ignoring unwanted exceptions::
>>> class ParserError(Exception):
... pass
...
>>> try:
... import audioop
... except ImportError:
... pass
...
Another place :keyword:`pass` 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, telling you exactly where the incomplete code
is. Note the two calling styles of the exceptions above.
The first style, with no message but with an accompanying comment,
lets you easily leave the comment when you remove the exception,
which ideally would be a good description for
the block of code the exception is a placeholder for. However, the
third example, providing a message for the exception, will produce
a more useful traceback.
.. _tut-functions: