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<dl><dd><pre class="verbatim">
p = pickle.Pickler(f)
p.dump(x)
</pre></dl>

<P>
A shorthand for this is:

<P>
<dl><dd><pre class="verbatim">
pickle.dump(x, f)
</pre></dl>

<P>
To unpickle an object <code>x</code> from a file <code>f</code>, open for reading:

<P>
<dl><dd><pre class="verbatim">
u = pickle.Unpickler(f)
x = u.load()
</pre></dl>

<P>
A shorthand is:

<P>
<dl><dd><pre class="verbatim">
x = pickle.load(f)
</pre></dl>

<P>
The <tt class="class">Pickler</tt> class only calls the method <code>f.write()</code> with a
string argument.  The <tt class="class">Unpickler</tt> calls the methods <code>f.read()</code>
(with an integer argument) and <code>f.readline()</code> (without argument),
both returning a string.  It is explicitly allowed to pass non-file
objects here, as long as they have the right methods.

<P>
The constructor for the <tt class="class">Pickler</tt> class has an optional second
argument, <var>bin</var>.  If this is present and true, the binary
pickle format is used; if it is absent or false, the (less efficient,
but backwards compatible) text pickle format is used.  The
<tt class="class">Unpickler</tt> class does not have an argument to distinguish
between binary and text pickle formats; it accepts either format.

<P>
The following types can be pickled:

<P>

<UL>
<LI><code>None</code>

<P>
</LI>
<LI>integers, long integers, floating point numbers

<P>
</LI>
<LI>normal and Unicode strings

<P>
</LI>
<LI>tuples, lists and dictionaries containing only picklable objects

<P>
</LI>
<LI>functions defined at the top level of a module (by name
      reference, not storage of the implementation)

<P>
</LI>
<LI>built-in functions

<P>
</LI>
<LI>classes that are defined at the top level in a module

<P>
</LI>
<LI>instances of such classes whose <tt class="member">__dict__</tt> or
<tt class="method">__setstate__()</tt> is picklable

<P>
</LI>
</UL>

<P>
Attempts to pickle unpicklable objects will raise the
<tt class="exception">PicklingError</tt> exception; when this happens, an unspecified
number of bytes may have been written to the file.

<P>
It is possible to make multiple calls to the <tt class="method">dump()</tt> method of
the same <tt class="class">Pickler</tt> instance.  These must then be matched to the
same number of calls to the <tt class="method">load()</tt> method of the
corresponding <tt class="class">Unpickler</tt> instance.  If the same object is
pickled by multiple <tt class="method">dump()</tt> calls, the <tt class="method">load()</tt> will all
yield references to the same object.  <i>Warning</i>: this is intended
for pickling multiple objects without intervening modifications to the
objects or their parts.  If you modify an object and then pickle it
again using the same <tt class="class">Pickler</tt> instance, the object is not
pickled again -- a reference to it is pickled and the
<tt class="class">Unpickler</tt> will return the old value, not the modified one.
(There are two problems here: (a) detecting changes, and (b)
marshalling a minimal set of changes.  I have no answers.  Garbage
Collection may also become a problem here.)

<P>
Apart from the <tt class="class">Pickler</tt> and <tt class="class">Unpickler</tt> classes, the
module defines the following functions, and an exception:

<P>
<dl><dt><b><a name='l2h-415'><tt class='function'>dump</tt></a></b> (<var>object, file</var><big>[</big><var>, bin</var><big>]</big>)
<dd>
Write a pickled representation of <var>object</var> to the open file object
<var>file</var>.  This is equivalent to
"<tt class="samp">Pickler(<var>file</var>, <var>bin</var>).dump(<var>object</var>)</tt>".
If the optional <var>bin</var> argument is present and nonzero, the binary
pickle format is used; if it is zero or absent, the (less efficient)
text pickle format is used.
</dl>

<P>
<dl><dt><b><a name='l2h-416'><tt class='function'>load</tt></a></b> (<var>file</var>)
<dd>
Read a pickled object from the open file object <var>file</var>.  This is
equivalent to "<tt class="samp">Unpickler(<var>file</var>).load()</tt>".
</dl>

<P>
<dl><dt><b><a name='l2h-417'><tt class='function'>dumps</tt></a></b> (<var>object</var><big>[</big><var>, bin</var><big>]</big>)
<dd>
Return the pickled representation of the object as a string, instead
of writing it to a file.  If the optional <var>bin</var> argument is
present and nonzero, the binary pickle format is used; if it is zero
or absent, the (less efficient) text pickle format is used.
</dl>

<P>
<dl><dt><b><a name='l2h-418'><tt class='function'>loads</tt></a></b> (<var>string</var>)
<dd>
Read a pickled object from a string instead of a file.  Characters in
the string past the pickled object's representation are ignored.
</dl>

<P>
<dl><dt><b><a name='l2h-419'><tt class='exception'>PicklingError</tt></a></b>
<dd>
This exception is raised when an unpicklable object is passed to
<tt class="method">Pickler.dump()</tt>.
</dl>

<P>
<div class='seealso'>
  <p class='heading'><b>See Also:</b></p>

  <dl compact class="seemodule">
    <dt>Module <b><tt class='module'><a href="module-copyreg.html" tppabs="http://www.python.org/doc/current/lib/module-copyreg.html">copy_reg</a></tt>:</b>
    <dd>pickle interface constructor
                                registration.
  </dl>

<P>
<dl compact class="seemodule">
    <dt>Module <b><tt class='module'><a href="module-shelve.html" tppabs="http://www.python.org/doc/current/lib/module-shelve.html">shelve</a></tt>:</b>
    <dd>indexed databases of objects; uses <tt class="module">pickle</tt>.
  </dl>

<P>
<dl compact class="seemodule">
    <dt>Module <b><tt class='module'><a href="module-copy.html" tppabs="http://www.python.org/doc/current/lib/module-copy.html">copy</a></tt>:</b>
    <dd>shallow and deep object copying.
  </dl>

<P>
<dl compact class="seemodule">
    <dt>Module <b><tt class='module'><a href="module-marshal.html" tppabs="http://www.python.org/doc/current/lib/module-marshal.html">marshal</a></tt>:</b>
    <dd>high-performance serialization of built-in types.
  </dl>
</div>

<P>

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