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clarify __getnewargs__ and __setstate__

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Mark Pilgrim
2009-08-16 20:27:37 -04:00
parent 1a9113d5da
commit 0ea4113d15
1 changed files with 4 additions and 2 deletions
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special-method-names.html
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@@ -703,16 +703,18 @@ class FieldStorage:
<td>to serialize an object (new pickling protocol)
<td><code class=pp>pickle.dump(x, <var>file</var>, <var>protocol_version</var>)</code>
<td><a href=http://docs.python.org/3.1/library/pickle.html#pickling-class-instances><code>x.<dfn>__reduce_ex__</dfn>(<var>protocol_version</var>)</code></a>
<tr><th>
<tr><th>*
<td>control over how an object is created during unpickling
<td><code class=pp>x = pickle.load(<var>file</var>)</code>
<td><a href=http://docs.python.org/3.1/library/pickle.html#pickling-class-instances><code>x.<dfn>__getnewargs__</dfn>()</code></a>
<tr><th>
<tr><th>*
<td>to restore an object&#8217;s state after unpickling
<td><code class=pp>x = pickle.load(<var>file</var>)</code>
<td><a href=http://docs.python.org/3.1/library/pickle.html#pickle-state><code>x.<dfn>__setstate__</dfn>()</code></a>
</table>
<p>* To recreate a serialized object, Python needs to create a new object that looks like the serialized object, then set the values of all the attributes on the new object. The <code>__getnewargs__()</code> method controls how the object is created, then the <code>__setstate__()</code> method controls how the attribute values are restored.
<h2 id=context-managers>Classes That Can Be Used in a <code>with</code> Block</h2>
<p>Python 3 supports the <code>with</code> statement, which allows you to access an object&#8217;s properties and methods without explicitly referencing the object every time. A <code>with</code> block defines a <a href=http://www.python.org/doc/3.1/library/stdtypes.html#typecontextmanager>runtime context</a>; you &#8220;enter&#8221; the context when you execute the <code>with</code> statement, and you &#8220;exit&#8221; the context after you execute the last statement in the block.