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<H2><A NAME="SECTION0051430000000000000000">
3.14.3 Usage</A>
</H2>

<P>
To serialize an object hierarchy, you first create a pickler, then you
call the pickler's <tt class="method">dump()</tt> method.  To de-serialize a data
stream, you first create an unpickler, then you call the unpickler's
<tt class="method">load()</tt> method.  The <tt class="module">pickle</tt> module provides the
following constant:

<P>
<dl><dt><b><tt id='l2h-633' xml:id='l2h-633'>HIGHEST_PROTOCOL</tt></b></dt>
<dd>
The highest protocol version available.  This value can be passed
as a <var>protocol</var> value.

<span class="versionnote">New in version 2.3.</span>

</dd></dl>

<P>
The <tt class="module">pickle</tt> module provides the
following functions to make this process more convenient:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-634' xml:id='l2h-634' class="function">dump</tt></b>(</nobr></td>
  <td><var>obj, file</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Write a pickled representation of <var>obj</var> to the open file object
<var>file</var>.  This is equivalent to
<code>Pickler(<var>file</var>, <var>protocol</var>, <var>bin</var>).dump(<var>obj</var>)</code>.

<P>
If the <var>protocol</var> parameter is omitted, protocol 0 is used.
If <var>protocol</var> is specified as a negative value
or <tt class="constant">HIGHEST_PROTOCOL</tt>,
the highest protocol version will be used.

<P>

<span class="versionnote">Changed in version 2.3:
The <var>protocol</var> parameter was added.
The <var>bin</var> parameter is deprecated and only provided
for backwards compatibility.  You should use the <var>protocol</var>
parameter instead.</span>

<P>
If the optional <var>bin</var> argument is true, the binary pickle format
is used; otherwise the (less efficient) text pickle format is used
(for backwards compatibility, this is the default).

<P>
<var>file</var> must have a <tt class="method">write()</tt> method that accepts a single
string argument.  It can thus be a file object opened for writing, a
<tt class="module"><a href="module-StringIO.html">StringIO</a></tt> object, or any other custom
object that meets this interface.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-635' xml:id='l2h-635' class="function">load</tt></b>(</nobr></td>
  <td><var>file</var>)</td></tr></table></dt>
<dd>
Read a string from the open file object <var>file</var> and interpret it as
a pickle data stream, reconstructing and returning the original object
hierarchy.  This is equivalent to <code>Unpickler(<var>file</var>).load()</code>.

<P>
<var>file</var> must have two methods, a <tt class="method">read()</tt> method that takes
an integer argument, and a <tt class="method">readline()</tt> method that requires no
arguments.  Both methods should return a string.  Thus <var>file</var> can
be a file object opened for reading, a
<tt class="module">StringIO</tt> object, or any other custom
object that meets this interface.

<P>
This function automatically determines whether the data stream was
written in binary mode or not.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-636' xml:id='l2h-636' class="function">dumps</tt></b>(</nobr></td>
  <td><var>obj</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
Return the pickled representation of the object as a string, instead
of writing it to a file.

<P>
If the <var>protocol</var> parameter is omitted, protocol 0 is used.
If <var>protocol</var> is specified as a negative value
or <tt class="constant">HIGHEST_PROTOCOL</tt>,
the highest protocol version will be used.

<P>

<span class="versionnote">Changed in version 2.3:
The <var>protocol</var> parameter was added.
The <var>bin</var> parameter is deprecated and only provided
for backwards compatibility.  You should use the <var>protocol</var>
parameter instead.</span>

<P>
If the optional <var>bin</var> argument is
true, the binary pickle format is used; otherwise the (less efficient)
text pickle format is used (this is the default).
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-637' xml:id='l2h-637' class="function">loads</tt></b>(</nobr></td>
  <td><var>string</var>)</td></tr></table></dt>
<dd>
Read a pickled object hierarchy from a string.  Characters in the
string past the pickled object's representation are ignored.
</dl>

<P>
The <tt class="module">pickle</tt> module also defines three exceptions:

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-638' xml:id='l2h-638' class="exception">PickleError</tt></b></dt>
<dd>
A common base class for the other exceptions defined below.  This
inherits from <tt class="exception">Exception</tt>.
</dd></dl>

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-639' xml:id='l2h-639' class="exception">PicklingError</tt></b></dt>
<dd>
This exception is raised when an unpicklable object is passed to
the <tt class="method">dump()</tt> method.
</dd></dl>

<P>
<dl><dt><b><span class="typelabel">exception</span>&nbsp;<tt id='l2h-640' xml:id='l2h-640' class="exception">UnpicklingError</tt></b></dt>
<dd>
This exception is raised when there is a problem unpickling an object.
Note that other exceptions may also be raised during unpickling,
including (but not necessarily limited to) <tt class="exception">AttributeError</tt>,
<tt class="exception">EOFError</tt>, <tt class="exception">ImportError</tt>, and <tt class="exception">IndexError</tt>.
</dd></dl>

<P>
The <tt class="module">pickle</tt> module also exports two callables<A NAME="tex2html15"
  HREF="#foot8968"><SUP>3.3</SUP></A>, <tt class="class">Pickler</tt> and <tt class="class">Unpickler</tt>:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-641' xml:id='l2h-641' class="class">Pickler</tt></b>(</nobr></td>
  <td><var>file</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
<dd>
This takes a file-like object to which it will write a pickle data
stream.  

<P>
If the <var>protocol</var> parameter is omitted, protocol 0 is used.
If <var>protocol</var> is specified as a negative value,
the highest protocol version will be used.

<P>

<span class="versionnote">Changed in version 2.3:
The <var>bin</var> parameter is deprecated and only provided
for backwards compatibility.  You should use the <var>protocol</var>
parameter instead.</span>

<P>
Optional <var>bin</var> if true, tells the pickler to use the more
efficient binary pickle format, otherwise the ASCII format is used
(this is the default).

<P>
<var>file</var> must have a <tt class="method">write()</tt> method that accepts a single
string argument.  It can thus be an open file object, a
<tt class="module">StringIO</tt> object, or any other custom
object that meets this interface.
</dl>

<P>
<tt class="class">Pickler</tt> objects define one (or two) public methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-642' xml:id='l2h-642' class="method">dump</tt></b>(</nobr></td>
  <td><var>obj</var>)</td></tr></table></dt>
<dd>
Write a pickled representation of <var>obj</var> to the open file object
given in the constructor.  Either the binary or ASCII format will
be used, depending on the value of the <var>bin</var> flag passed to the
constructor.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-643' xml:id='l2h-643' class="method">clear_memo</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Clears the pickler's ``memo''.  The memo is the data structure that
remembers which objects the pickler has already seen, so that shared
or recursive objects pickled by reference and not by value.  This
method is useful when re-using picklers.

<P>
<div class="note"><b class="label">Note:</b>
Prior to Python 2.3, <tt class="method">clear_memo()</tt> was only available on the
picklers created by <tt class="module"><a href="module-cPickle.html">cPickle</a></tt>.  In the <tt class="module">pickle</tt> module,
picklers have an instance variable called <tt class="member">memo</tt> which is a
Python dictionary.  So to clear the memo for a <tt class="module">pickle</tt> module
pickler, you could do the following:

<P>
<div class="verbatim"><pre>
mypickler.memo.clear()
</pre></div>

<P>
Code that does not need to support older versions of Python should
simply use <tt class="method">clear_memo()</tt>.
</div>
</dl>

<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.<A NAME="tex2html16"
  HREF="#foot8970"><SUP>3.4</SUP></A>
<P>
<tt class="class">Unpickler</tt> objects are defined as:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><span class="typelabel">class</span>&nbsp;<tt id='l2h-644' xml:id='l2h-644' class="class">Unpickler</tt></b>(</nobr></td>
  <td><var>file</var>)</td></tr></table></dt>
<dd>
This takes a file-like object from which it will read a pickle data
stream.  This class automatically determines whether the data stream
was written in binary mode or not, so it does not need a flag as in
the <tt class="class">Pickler</tt> factory.

<P>
<var>file</var> must have two methods, a <tt class="method">read()</tt> method that takes
an integer argument, and a <tt class="method">readline()</tt> method that requires no
arguments.  Both methods should return a string.  Thus <var>file</var> can
be a file object opened for reading, a
<tt class="module">StringIO</tt> object, or any other custom
object that meets this interface.
</dl>

<P>
<tt class="class">Unpickler</tt> objects have one (or two) public methods:

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-645' xml:id='l2h-645' class="method">load</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
Read a pickled object representation from the open file object given
in the constructor, and return the reconstituted object hierarchy
specified therein.
</dl>

<P>
<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
  <td><nobr><b><tt id='l2h-646' xml:id='l2h-646' class="method">noload</tt></b>(</nobr></td>
  <td><var></var>)</td></tr></table></dt>
<dd>
This is just like <tt class="method">load()</tt> except that it doesn't actually
create any objects.  This is useful primarily for finding what's
called ``persistent ids'' that may be referenced in a pickle data
stream.  See section&nbsp;<A href="pickle-protocol.html#pickle-protocol">3.14.5</A> below for more details.

<P>
<strong>Note:</strong> the <tt class="method">noload()</tt> method is currently only
available on <tt class="class">Unpickler</tt> objects created with the
<tt class="module">cPickle</tt> module.  <tt class="module">pickle</tt> module <tt class="class">Unpickler</tt>s do
not have the <tt class="method">noload()</tt> method.
</dl>

<P>
<BR><HR><H4>Footnotes</H4>
<DL>
<DT><A NAME="foot8968">... callables</A><A
 HREF="node65.html#tex2html15"><SUP>3.3</SUP></A></DT>
<DD>In the
<tt class="module">pickle</tt> module these callables are classes, which you could
subclass to customize the behavior.  However, in the <tt class="module"><a href="module-cPickle.html">cPickle</a></tt>
module these callables are factory functions and so cannot be
subclassed.  One common reason to subclass is to control what
objects can actually be unpickled.  See section&nbsp;<A href="pickle-sub.html#pickle-sub">3.14.6</A> for
more details.

</DD>
<DT><A NAME="foot8970">... object.</A><A
 HREF="node65.html#tex2html16"><SUP>3.4</SUP></A></DT>
<DD><em>Warning</em>: 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: (1) detecting changes, and (2)
marshalling a minimal set of changes.  Garbage Collection may also
become a problem here.

</DD>
</DL>
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	54
	55	<H2><A NAME="SECTION0051430000000000000000">
	56	3.14.3 Usage</A>
	57	</H2>
	58
	59	<P>
	60	To serialize an object hierarchy, you first create a pickler, then you
	61	call the pickler's <tt class="method">dump()</tt> method. To de-serialize a data
	62	stream, you first create an unpickler, then you call the unpickler's
	63	<tt class="method">load()</tt> method. The <tt class="module">pickle</tt> module provides the
	64	following constant:
65
66	<P>
67	<dl><dt><b><tt id='l2h-633' xml:id='l2h-633'>HIGHEST_PROTOCOL</tt></b></dt>
68	<dd>
69	The highest protocol version available. This value can be passed
70	as a <var>protocol</var> value.
71
72	<span class="versionnote">New in version 2.3.</span>
73
74	</dd></dl>
75
76	<P>
77	The <tt class="module">pickle</tt> module provides the
78	following functions to make this process more convenient:
79
80	<P>
81	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
82	<td><nobr><b><tt id='l2h-634' xml:id='l2h-634' class="function">dump</tt></b>(</nobr></td>
83	<td><var>obj, file</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
84	<dd>
85	Write a pickled representation of <var>obj</var> to the open file object
86	<var>file</var>. This is equivalent to
87	<code>Pickler(<var>file</var>, <var>protocol</var>, <var>bin</var>).dump(<var>obj</var>)</code>.
88
89	<P>
90	If the <var>protocol</var> parameter is omitted, protocol 0 is used.
91	If <var>protocol</var> is specified as a negative value
92	or <tt class="constant">HIGHEST_PROTOCOL</tt>,
93	the highest protocol version will be used.
94
95	<P>
96
97	<span class="versionnote">Changed in version 2.3:
98	The <var>protocol</var> parameter was added.
99	The <var>bin</var> parameter is deprecated and only provided
100	for backwards compatibility. You should use the <var>protocol</var>
101	parameter instead.</span>
102
103	<P>
104	If the optional <var>bin</var> argument is true, the binary pickle format
105	is used; otherwise the (less efficient) text pickle format is used
106	(for backwards compatibility, this is the default).
107
108	<P>
109	<var>file</var> must have a <tt class="method">write()</tt> method that accepts a single
110	string argument. It can thus be a file object opened for writing, a
111	<tt class="module"><a href="module-StringIO.html">StringIO</a></tt> object, or any other custom
112	object that meets this interface.
113	</dl>
114
115	<P>
116	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
117	<td><nobr><b><tt id='l2h-635' xml:id='l2h-635' class="function">load</tt></b>(</nobr></td>
118	<td><var>file</var>)</td></tr></table></dt>
119	<dd>
120	Read a string from the open file object <var>file</var> and interpret it as
121	a pickle data stream, reconstructing and returning the original object
122	hierarchy. This is equivalent to <code>Unpickler(<var>file</var>).load()</code>.
123
124	<P>
125	<var>file</var> must have two methods, a <tt class="method">read()</tt> method that takes
126	an integer argument, and a <tt class="method">readline()</tt> method that requires no
127	arguments. Both methods should return a string. Thus <var>file</var> can
128	be a file object opened for reading, a
129	<tt class="module">StringIO</tt> object, or any other custom
130	object that meets this interface.
131
132	<P>
133	This function automatically determines whether the data stream was
134	written in binary mode or not.
135	</dl>
136
137	<P>
138	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
139	<td><nobr><b><tt id='l2h-636' xml:id='l2h-636' class="function">dumps</tt></b>(</nobr></td>
140	<td><var>obj</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
141	<dd>
142	Return the pickled representation of the object as a string, instead
143	of writing it to a file.
144
145	<P>
146	If the <var>protocol</var> parameter is omitted, protocol 0 is used.
147	If <var>protocol</var> is specified as a negative value
148	or <tt class="constant">HIGHEST_PROTOCOL</tt>,
149	the highest protocol version will be used.
150
151	<P>
152
153	<span class="versionnote">Changed in version 2.3:
154	The <var>protocol</var> parameter was added.
155	The <var>bin</var> parameter is deprecated and only provided
156	for backwards compatibility. You should use the <var>protocol</var>
157	parameter instead.</span>
158
159	<P>
160	If the optional <var>bin</var> argument is
161	true, the binary pickle format is used; otherwise the (less efficient)
162	text pickle format is used (this is the default).
163	</dl>
164
165	<P>
166	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
167	<td><nobr><b><tt id='l2h-637' xml:id='l2h-637' class="function">loads</tt></b>(</nobr></td>
168	<td><var>string</var>)</td></tr></table></dt>
169	<dd>
170	Read a pickled object hierarchy from a string. Characters in the
171	string past the pickled object's representation are ignored.
172	</dl>
173
174	<P>
175	The <tt class="module">pickle</tt> module also defines three exceptions:
176
177	<P>
178	<dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-638' xml:id='l2h-638' class="exception">PickleError</tt></b></dt>
179	<dd>
180	A common base class for the other exceptions defined below. This
181	inherits from <tt class="exception">Exception</tt>.
182	</dd></dl>
183
184	<P>
185	<dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-639' xml:id='l2h-639' class="exception">PicklingError</tt></b></dt>
186	<dd>
187	This exception is raised when an unpicklable object is passed to
188	the <tt class="method">dump()</tt> method.
189	</dd></dl>
190
191	<P>
192	<dl><dt><b><span class="typelabel">exception</span> <tt id='l2h-640' xml:id='l2h-640' class="exception">UnpicklingError</tt></b></dt>
193	<dd>
194	This exception is raised when there is a problem unpickling an object.
195	Note that other exceptions may also be raised during unpickling,
196	including (but not necessarily limited to) <tt class="exception">AttributeError</tt>,
197	<tt class="exception">EOFError</tt>, <tt class="exception">ImportError</tt>, and <tt class="exception">IndexError</tt>.
198	</dd></dl>
199
200	<P>
201	The <tt class="module">pickle</tt> module also exports two callables<A NAME="tex2html15"
202	HREF="#foot8968"><SUP>3.3</SUP></A>, <tt class="class">Pickler</tt> and <tt class="class">Unpickler</tt>:
203
204	<P>
205	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
206	<td><nobr><b><span class="typelabel">class</span> <tt id='l2h-641' xml:id='l2h-641' class="class">Pickler</tt></b>(</nobr></td>
207	<td><var>file</var><big>[</big><var>, protocol</var><big>[</big><var>, bin</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt>
208	<dd>
209	This takes a file-like object to which it will write a pickle data
210	stream.
211
212	<P>
213	If the <var>protocol</var> parameter is omitted, protocol 0 is used.
214	If <var>protocol</var> is specified as a negative value,
215	the highest protocol version will be used.
216
217	<P>
218
219	<span class="versionnote">Changed in version 2.3:
220	The <var>bin</var> parameter is deprecated and only provided
221	for backwards compatibility. You should use the <var>protocol</var>
222	parameter instead.</span>
223
224	<P>
225	Optional <var>bin</var> if true, tells the pickler to use the more
226	efficient binary pickle format, otherwise the ASCII format is used
227	(this is the default).
228
229	<P>
230	<var>file</var> must have a <tt class="method">write()</tt> method that accepts a single
231	string argument. It can thus be an open file object, a
232	<tt class="module">StringIO</tt> object, or any other custom
233	object that meets this interface.
234	</dl>
235
236	<P>
237	<tt class="class">Pickler</tt> objects define one (or two) public methods:
238
239	<P>
240	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
241	<td><nobr><b><tt id='l2h-642' xml:id='l2h-642' class="method">dump</tt></b>(</nobr></td>
242	<td><var>obj</var>)</td></tr></table></dt>
243	<dd>
244	Write a pickled representation of <var>obj</var> to the open file object
245	given in the constructor. Either the binary or ASCII format will
246	be used, depending on the value of the <var>bin</var> flag passed to the
247	constructor.
248	</dl>
249
250	<P>
251	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
252	<td><nobr><b><tt id='l2h-643' xml:id='l2h-643' class="method">clear_memo</tt></b>(</nobr></td>
253	<td><var></var>)</td></tr></table></dt>
254	<dd>
255	Clears the pickler's ``memo''. The memo is the data structure that
256	remembers which objects the pickler has already seen, so that shared
257	or recursive objects pickled by reference and not by value. This
258	method is useful when re-using picklers.
259
260	<P>
261	<div class="note"><b class="label">Note:</b>
262	Prior to Python 2.3, <tt class="method">clear_memo()</tt> was only available on the
263	picklers created by <tt class="module"><a href="module-cPickle.html">cPickle</a></tt>. In the <tt class="module">pickle</tt> module,
264	picklers have an instance variable called <tt class="member">memo</tt> which is a
265	Python dictionary. So to clear the memo for a <tt class="module">pickle</tt> module
266	pickler, you could do the following:
267
268	<P>
269	<div class="verbatim"><pre>
270	mypickler.memo.clear()
271	</pre></div>
272
273	<P>
274	Code that does not need to support older versions of Python should
275	simply use <tt class="method">clear_memo()</tt>.
276	</div>
277	</dl>
278
279	<P>
280	It is possible to make multiple calls to the <tt class="method">dump()</tt> method of
281	the same <tt class="class">Pickler</tt> instance. These must then be matched to the
282	same number of calls to the <tt class="method">load()</tt> method of the
283	corresponding <tt class="class">Unpickler</tt> instance. If the same object is
284	pickled by multiple <tt class="method">dump()</tt> calls, the <tt class="method">load()</tt> will
285	all yield references to the same object.<A NAME="tex2html16"
286	HREF="#foot8970"><SUP>3.4</SUP></A>
287	<P>
288	<tt class="class">Unpickler</tt> objects are defined as:
289
290	<P>
291	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
292	<td><nobr><b><span class="typelabel">class</span> <tt id='l2h-644' xml:id='l2h-644' class="class">Unpickler</tt></b>(</nobr></td>
293	<td><var>file</var>)</td></tr></table></dt>
294	<dd>
295	This takes a file-like object from which it will read a pickle data
296	stream. This class automatically determines whether the data stream
297	was written in binary mode or not, so it does not need a flag as in
298	the <tt class="class">Pickler</tt> factory.
299
300	<P>
301	<var>file</var> must have two methods, a <tt class="method">read()</tt> method that takes
302	an integer argument, and a <tt class="method">readline()</tt> method that requires no
303	arguments. Both methods should return a string. Thus <var>file</var> can
304	be a file object opened for reading, a
305	<tt class="module">StringIO</tt> object, or any other custom
306	object that meets this interface.
307	</dl>
308
309	<P>
310	<tt class="class">Unpickler</tt> objects have one (or two) public methods:
311
312	<P>
313	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
314	<td><nobr><b><tt id='l2h-645' xml:id='l2h-645' class="method">load</tt></b>(</nobr></td>
315	<td><var></var>)</td></tr></table></dt>
316	<dd>
317	Read a pickled object representation from the open file object given
318	in the constructor, and return the reconstituted object hierarchy
319	specified therein.
320	</dl>
321
322	<P>
323	<dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline">
324	<td><nobr><b><tt id='l2h-646' xml:id='l2h-646' class="method">noload</tt></b>(</nobr></td>
325	<td><var></var>)</td></tr></table></dt>
326	<dd>
327	This is just like <tt class="method">load()</tt> except that it doesn't actually
328	create any objects. This is useful primarily for finding what's
329	called ``persistent ids'' that may be referenced in a pickle data
330	stream. See section <A href="pickle-protocol.html#pickle-protocol">3.14.5</A> below for more details.
331
332	<P>
333	<strong>Note:</strong> the <tt class="method">noload()</tt> method is currently only
334	available on <tt class="class">Unpickler</tt> objects created with the
335	<tt class="module">cPickle</tt> module. <tt class="module">pickle</tt> module <tt class="class">Unpickler</tt>s do
336	not have the <tt class="method">noload()</tt> method.
337	</dl>
338
339	<P>
340	<BR><HR><H4>Footnotes</H4>
341	<DL>
342	<DT><A NAME="foot8968">... callables</A><A
343	HREF="node65.html#tex2html15"><SUP>3.3</SUP></A></DT>
344	<DD>In the
345	<tt class="module">pickle</tt> module these callables are classes, which you could
346	subclass to customize the behavior. However, in the <tt class="module"><a href="module-cPickle.html">cPickle</a></tt>
347	module these callables are factory functions and so cannot be
348	subclassed. One common reason to subclass is to control what
349	objects can actually be unpickled. See section <A href="pickle-sub.html#pickle-sub">3.14.6</A> for
350	more details.
351
352	</DD>
353	<DT><A NAME="foot8970">... object.</A><A
354	HREF="node65.html#tex2html16"><SUP>3.4</SUP></A></DT>
355	<DD><em>Warning</em>: this
356	is intended for pickling multiple objects without intervening
357	modifications to the objects or their parts. If you modify an object
358	and then pickle it again using the same <tt class="class">Pickler</tt> instance, the
359	object is not pickled again -- a reference to it is pickled and the
360	<tt class="class">Unpickler</tt> will return the old value, not the modified one.
361	There are two problems here: (1) detecting changes, and (2)
362	marshalling a minimal set of changes. Garbage Collection may also
363	become a problem here.
364
365	</DD>
366	</DL>
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