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a few refinements

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[SVN r15072]
This commit is contained in:
Ralf W. Grosse-Kunstleve
2002-08-23 22:34:05 +00:00
parent 0bbfa9b483
commit 1ee7bd2a60
1 changed files with 15 additions and 17 deletions
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doc/v2/pickle.html
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@@ -173,7 +173,7 @@ provide pickle support.
For simplicity, the <tt>__dict__</tt> is not included in the result
of <tt>__getstate__</tt>. This is not generally recommended, but a
valid approach if it is anticipated that the object's
<tt>__dict__</tt> will always be empty. Note that the safet guard
<tt>__dict__</tt> will always be empty. Note that the safety guard
described below will catch the cases where this assumption is violated.
<hr>
@@ -188,24 +188,15 @@ provide pickle support.
<hr>
<h2>Pitfall and Safety Guard</h2>
In Boost.Python extension modules with many extension classes,
providing complete pickle support for all classes would be a
significant overhead. In general complete pickle support should only be
implemented for extension classes that will eventually be pickled.
However, the author of a Boost.Python extension module might not
anticipate correctly which classes need support for pickle.
Unfortunately, the pickle protocol described above has an important
pitfall that the end user of a Boost.Python extension module might not
be aware of:
<dl>
<dt>
The pickle protocol described above has an important pitfall that the
end user of a Boost.Python extension module might not be aware of:
<p>
<strong>
<tt>__getstate__</tt> is defined and the instance's <tt>__dict__</tt>
is not empty.
</strong>
<p>
<dd>
The author of a Boost.Python extension class might provide a
<tt>__getstate__</tt> method without considering the possibilities
that:
@@ -239,9 +230,9 @@ is not empty.
To resolve this problem, it should first be established that the
<tt>__getstate__</tt> and <tt>__setstate__</tt> methods manage the
instances's <tt>__dict__</tt> correctly. Note that this can be done
both at the C++ and the Python level. Finally, the safety guard
either at the C++ or the Python level. Finally, the safety guard
should intentionally be overridden. E.g. in C++ (from
<a href="../../test/pickle3.cpp"><tt>pickle3.cpp</tt></a>:
<a href="../../test/pickle3.cpp"><tt>pickle3.cpp</tt></a>):
<pre>
struct world_pickle_suite : boost::python::pickle_suite
@@ -263,12 +254,19 @@ is not empty.
def __setstate__(self, state):
# your code here
</pre>
</dl>
<hr>
<h2>Practical Advice</h2>
<ul>
<li>
In Boost.Python extension modules with many extension classes,
providing complete pickle support for all classes would be a
significant overhead. In general complete pickle support should
only be implemented for extension classes that will eventually
be pickled.
<p>
<li>
Avoid using <tt>__getstate__</tt> if the instance can also be
reconstructed by way of <tt>__getinitargs__</tt>. This automatically