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<LI><A href="node13.html#SECTION0001310000000000000000">12.1 cookielib</a>
<LI><A href="node13.html#SECTION0001320000000000000000">12.2 doctest</a>
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<H1><A NAME="SECTION0001300000000000000000">
12 New, Improved, and Deprecated Modules</A>
</H1>

<P>
As usual, Python's standard library received a number of enhancements and
bug fixes.  Here's a partial list of the most notable changes, sorted
alphabetically by module name. Consult the
<span class="file">Misc/NEWS</span> file in the source tree for a more
complete list of changes, or look through the CVS logs for all the
details.

<P>

<UL>
<LI>The <tt class="module">asyncore</tt> module's <tt class="function">loop()</tt> function now
   has a <var>count</var> parameter that lets you perform a limited number
   of passes through the polling loop.  The default is still to loop
   forever.

<P>
</LI>
<LI>The <tt class="module">base64</tt> module now has more complete RFC 3548 support
  for Base64, Base32, and Base16 encoding and decoding, including
  optional case folding and optional alternative alphabets.
  (Contributed by Barry Warsaw.)

<P>
</LI>
<LI>The <tt class="module">bisect</tt> module now has an underlying C implementation
   for improved performance.
   (Contributed by Dmitry Vasiliev.)

<P>
</LI>
<LI>The CJKCodecs collections of East Asian codecs, maintained
by Hye-Shik Chang, was integrated into 2.4.  
The new encodings are:

<P>

<UL>
<LI>Chinese (PRC): gb2312, gbk, gb18030, big5hkscs, hz
</LI>
<LI>Chinese (ROC): big5, cp950
</LI>
<LI>Japanese: cp932, euc-jis-2004, euc-jp,
euc-jisx0213, iso-2022-jp, iso-2022-jp-1, iso-2022-jp-2,
 iso-2022-jp-3, iso-2022-jp-ext, iso-2022-jp-2004,
 shift-jis, shift-jisx0213, shift-jis-2004
</LI>
<LI>Korean: cp949, euc-kr, johab, iso-2022-kr
</LI>
</UL> 

<P>
</LI>
<LI>Some other new encodings were added: HP Roman8, 
ISO_8859-11, ISO_8859-16, PCTP-154, and TIS-620.

<P>
</LI>
<LI>The UTF-8 and UTF-16 codecs now cope better with receiving partial input.
Previously the <tt class="class">StreamReader</tt> class would try to read more data,
making it impossible to resume decoding from the stream.  The
<tt class="method">read()</tt> method will now return as much data as it can and future
calls will resume decoding where previous ones left off. 
(Implemented by Walter D&#246;rwald.)

<P>
</LI>
<LI>There is a new <tt class="module">collections</tt> module for 
   various specialized collection datatypes.  
   Currently it contains just one type, <tt class="class">deque</tt>, 
   a double-ended queue that supports efficiently adding and removing
   elements from either end:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; from collections import deque
&gt;&gt;&gt; d = deque('ghi')        # make a new deque with three items
&gt;&gt;&gt; d.append('j')           # add a new entry to the right side
&gt;&gt;&gt; d.appendleft('f')       # add a new entry to the left side
&gt;&gt;&gt; d                       # show the representation of the deque
deque(['f', 'g', 'h', 'i', 'j'])
&gt;&gt;&gt; d.pop()                 # return and remove the rightmost item
'j'
&gt;&gt;&gt; d.popleft()             # return and remove the leftmost item
'f'
&gt;&gt;&gt; list(d)                 # list the contents of the deque
['g', 'h', 'i']
&gt;&gt;&gt; 'h' in d                # search the deque
True
</pre></div>

<P>
Several modules, such as the <tt class="module">Queue</tt> and <tt class="module">threading</tt>
modules, now take advantage of <tt class="class">collections.deque</tt> for improved
performance.  (Contributed by Raymond Hettinger.)

<P>
</LI>
<LI>The <tt class="module">ConfigParser</tt> classes have been enhanced slightly.
   The <tt class="method">read()</tt> method now returns a list of the files that
   were successfully parsed, and the <tt class="method">set()</tt> method raises
   <tt class="exception">TypeError</tt> if passed a <var>value</var> argument that isn't a
   string.   (Contributed by John Belmonte and David Goodger.)

<P>
</LI>
<LI>The <tt class="module">curses</tt> module now supports the ncurses extension 
   <tt class="function">use_default_colors()</tt>.  On platforms where the terminal
   supports transparency, this makes it possible to use a transparent
   background.  (Contributed by J&#246;rg Lehmann.)

<P>
</LI>
<LI>The <tt class="module">difflib</tt> module now includes an <tt class="class">HtmlDiff</tt> class
that creates an HTML table showing a side by side comparison
of two versions of a text.   (Contributed by Dan Gass.)

<P>
</LI>
<LI>The <tt class="module">email</tt> package was updated to version 3.0, 
which dropped various deprecated APIs and removes support for Python
versions earlier than 2.3.  The 3.0 version of the package uses a new
incremental parser for MIME messages, available in the
<tt class="module">email.FeedParser</tt> module.  The new parser doesn't require
reading the entire message into memory, and doesn't throw exceptions
if a message is malformed; instead it records any problems in the 
<tt class="member">defect</tt> attribute of the message.  (Developed by Anthony
Baxter, Barry Warsaw, Thomas Wouters, and others.)

<P>
</LI>
<LI>The <tt class="module">heapq</tt> module has been converted to C.  The resulting
   tenfold improvement in speed makes the module suitable for handling
   high volumes of data.  In addition, the module has two new functions
   <tt class="function">nlargest()</tt> and <tt class="function">nsmallest()</tt> that use heaps to
   find the N largest or smallest values in a dataset without the
   expense of a full sort.  (Contributed by Raymond Hettinger.)

<P>
</LI>
<LI>The <tt class="module">httplib</tt> module now contains constants for HTTP
status codes defined in various HTTP-related RFC documents.  Constants
have names such as <tt class="constant">OK</tt>, <tt class="constant">CREATED</tt>,
<tt class="constant">CONTINUE</tt>, and <tt class="constant">MOVED_PERMANENTLY</tt>; use pydoc to
get a full list.  (Contributed by Andrew Eland.)

<P>
</LI>
<LI>The <tt class="module">imaplib</tt> module now supports IMAP's THREAD command
(contributed by Yves Dionne) and new <tt class="method">deleteacl()</tt> and
<tt class="method">myrights()</tt> methods (contributed by Arnaud Mazin).

<P>
</LI>
<LI>The <tt class="module">itertools</tt> module gained a
  <tt class="function">groupby(<var>iterable</var><big>[</big>, <var>func</var><big>]</big>)</tt> function.
  <var>iterable</var> is something that can be iterated over to return a
  stream of elements, and the optional <var>func</var> parameter is a
  function that takes an element and returns a key value; if omitted,
  the key is simply the element itself.  <tt class="function">groupby()</tt> then
  groups the elements into subsequences which have matching values of
  the key, and returns a series of 2-tuples containing the key value
  and an iterator over the subsequence.

<P>
Here's an example to make this clearer.  The <var>key</var> function simply
returns whether a number is even or odd, so the result of
<tt class="function">groupby()</tt> is to return consecutive runs of odd or even
numbers.

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; import itertools
&gt;&gt;&gt; L = [2, 4, 6, 7, 8, 9, 11, 12, 14]
&gt;&gt;&gt; for key_val, it in itertools.groupby(L, lambda x: x % 2):
...    print key_val, list(it)
... 
0 [2, 4, 6]
1 [7]
0 [8]
1 [9, 11]
0 [12, 14]
&gt;&gt;&gt;
</pre></div>

<P>
<tt class="function">groupby()</tt> is typically used with sorted input.  The logic
for <tt class="function">groupby()</tt> is similar to the <span class="Unix">Unix</span> <code>uniq</code> filter
which makes it handy for eliminating, counting, or identifying
duplicate elements:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; word = 'abracadabra'
&gt;&gt;&gt; letters = sorted(word)   # Turn string into a sorted list of letters
&gt;&gt;&gt; letters 
['a', 'a', 'a', 'a', 'a', 'b', 'b', 'c', 'd', 'r', 'r']
&gt;&gt;&gt; for k, g in itertools.groupby(letters):
...    print k, list(g)
... 
a ['a', 'a', 'a', 'a', 'a']
b ['b', 'b']
c ['c']
d ['d']
r ['r', 'r']
&gt;&gt;&gt; # List unique letters
&gt;&gt;&gt; [k for k, g in groupby(letters)]                     
['a', 'b', 'c', 'd', 'r']
&gt;&gt;&gt; # Count letter occurrences
&gt;&gt;&gt; [(k, len(list(g))) for k, g in groupby(letters)]     
[('a', 5), ('b', 2), ('c', 1), ('d', 1), ('r', 2)]
</pre></div>

<P>
(Contributed by Hye-Shik Chang.)

<P>
</LI>
<LI><tt class="module">itertools</tt> also gained a function named
<tt class="function">tee(<var>iterator</var>, <var>N</var>)</tt> that returns <var>N</var> independent
iterators that replicate <var>iterator</var>.  If <var>N</var> is omitted, the
default is 2.

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; L = [1,2,3]
&gt;&gt;&gt; i1, i2 = itertools.tee(L)
&gt;&gt;&gt; i1,i2
(&lt;itertools.tee object at 0x402c2080&gt;, &lt;itertools.tee object at 0x402c2090&gt;)
&gt;&gt;&gt; list(i1)               # Run the first iterator to exhaustion
[1, 2, 3]
&gt;&gt;&gt; list(i2)               # Run the second iterator to exhaustion
[1, 2, 3]
&gt;
</pre></div>

<P>
Note that <tt class="function">tee()</tt> has to keep copies of the values returned 
by the iterator; in the worst case, it may need to keep all of them.  
This should therefore be used carefully if the leading iterator
can run far ahead of the trailing iterator in a long stream of inputs.
If the separation is large, then you might as well use 
<tt class="function">list()</tt> instead.  When the iterators track closely with one
another, <tt class="function">tee()</tt> is ideal.  Possible applications include
bookmarking, windowing, or lookahead iterators.
(Contributed by Raymond Hettinger.)       

<P>
</LI>
<LI>A number of functions were added to the <tt class="module">locale</tt> 
module, such as <tt class="function">bind_textdomain_codeset()</tt> to specify a
particular encoding and a family of <tt class="function">l*gettext()</tt> functions
that return messages in the chosen encoding.
(Contributed by Gustavo Niemeyer.)

<P>
</LI>
<LI>Some keyword arguments were added to the <tt class="module">logging</tt>
package's <tt class="function">basicConfig</tt> function to simplify log
configuration.  The default behavior is to log messages to standard
error, but various keyword arguments can be specified to log to a
particular file, change the logging format, or set the logging level.
For example:

<P>
<div class="verbatim"><pre>
import logging
logging.basicConfig(filename='/var/log/application.log',
    level=0,  # Log all messages
    format='%(levelname):%(process):%(thread):%(message)')	            
</pre></div>

<P>
Other additions to the <tt class="module">logging</tt> package include a
<tt class="method">log(<var>level</var>, <var>msg</var>)</tt> convenience method, as well as a
<tt class="class">TimedRotatingFileHandler</tt> class that rotates its log files at a
timed interval.  The module already had <tt class="class">RotatingFileHandler</tt>,
which rotated logs once the file exceeded a certain size.  Both
classes derive from a new <tt class="class">BaseRotatingHandler</tt> class that can
be used to implement other rotating handlers.

<P>
(Changes implemented by Vinay Sajip.)

<P>
</LI>
<LI>The <tt class="module">marshal</tt> module now shares interned strings on unpacking a 
data structure.  This may shrink the size of certain pickle strings,
but the primary effect is to make <span class="file">.pyc</span> files significantly smaller.
(Contributed by Martin von Loewis.)

<P>
</LI>
<LI>The <tt class="module">nntplib</tt> module's <tt class="class">NNTP</tt> class gained
<tt class="method">description()</tt> and <tt class="method">descriptions()</tt> methods to retrieve 
newsgroup descriptions for a single group or for a range of groups.
(Contributed by J&#252;rgen A. Erhard.)

<P>
</LI>
<LI>Two new functions were added to the <tt class="module">operator</tt> module, 
<tt class="function">attrgetter(<var>attr</var>)</tt> and <tt class="function">itemgetter(<var>index</var>)</tt>.
Both functions return callables that take a single argument and return
the corresponding attribute or item; these callables make excellent
data extractors when used with <tt class="function">map()</tt> or
<tt class="function">sorted()</tt>.  For example:

<P>
<div class="verbatim"><pre>
&gt;&gt;&gt; L = [('c', 2), ('d', 1), ('a', 4), ('b', 3)]
&gt;&gt;&gt; map(operator.itemgetter(0), L)
['c', 'd', 'a', 'b']
&gt;&gt;&gt; map(operator.itemgetter(1), L)
[2, 1, 4, 3]
&gt;&gt;&gt; sorted(L, key=operator.itemgetter(1)) # Sort list by second tuple item
[('d', 1), ('c', 2), ('b', 3), ('a', 4)]
</pre></div>

<P>
(Contributed by Raymond Hettinger.)       

<P>
</LI>
<LI>The <tt class="module">optparse</tt> module was updated in various ways.  The
module now passes its messages through <tt class="function">gettext.gettext()</tt>,
making it possible to internationalize Optik's help and error
messages.  Help messages for options can now include the string
<code>'%default'</code>, which will be replaced by the option's default
value.  (Contributed by Greg Ward.)

<P>
</LI>
<LI>The long-term plan is to deprecate the <tt class="module">rfc822</tt> module
in some future Python release in favor of the <tt class="module">email</tt> package.
To this end, the <tt class="function">email.Utils.formatdate()</tt> function has been
changed to make it usable as a replacement for
<tt class="function">rfc822.formatdate()</tt>.  You may want to write new e-mail
processing code with this in mind.  (Change implemented by Anthony
Baxter.)

<P>
</LI>
<LI>A new <tt class="function">urandom(<var>n</var>)</tt> function was added to the
<tt class="module">os</tt> module, returning a string containing <var>n</var> bytes of
random data.  This function provides access to platform-specific
sources of randomness such as <span class="file">/dev/urandom</span> on Linux or the
Windows CryptoAPI.  (Contributed by Trevor Perrin.)

<P>
</LI>
<LI>Another new function: <tt class="function">os.path.lexists(<var>path</var>)</tt> 
returns true if the file specified by <var>path</var> exists, whether or
not it's a symbolic link.  This differs from the existing
<tt class="function">os.path.exists(<var>path</var>)</tt> function, which returns false if 
<var>path</var> is a symlink that points to a destination that doesn't exist.
(Contributed by Beni Cherniavsky.)

<P>
</LI>
<LI>A new <tt class="function">getsid()</tt> function was added to the
<tt class="module">posix</tt> module that underlies the <tt class="module">os</tt> module.
(Contributed by J. Raynor.)

<P>
</LI>
<LI>The <tt class="module">poplib</tt> module now supports POP over SSL.  (Contributed by
Hector Urtubia.)

<P>
</LI>
<LI>The <tt class="module">profile</tt> module can now profile C extension functions.
(Contributed by Nick Bastin.)

<P>
</LI>
<LI>The <tt class="module">random</tt> module has a new method called
   <tt class="method">getrandbits(<var>N</var>)</tt> that returns a long integer <var>N</var>
   bits in length.  The existing <tt class="method">randrange()</tt> method now uses
   <tt class="method">getrandbits()</tt> where appropriate, making generation of
   arbitrarily large random numbers more efficient.  (Contributed by
   Raymond Hettinger.)

<P>
</LI>
<LI>The regular expression language accepted by the <tt class="module">re</tt> module
   was extended with simple conditional expressions, written as
   <tt class="regexp">(?(<var>group</var>)<var>A</var>|<var>B</var>)</tt>.  <var>group</var> is either a
   numeric group ID or a group name defined with <tt class="regexp">(?P&lt;group&gt;...)</tt> 
   earlier in the expression.  If the specified group matched, the
   regular expression pattern <var>A</var> will be tested against the string; if
   the group didn't match, the pattern <var>B</var> will be used instead.
   (Contributed by Gustavo Niemeyer.)

<P>
</LI>
<LI>The <tt class="module">re</tt> module is also no longer recursive, thanks to a
massive amount of work by Gustavo Niemeyer.  In a recursive regular
expression engine, certain patterns result in a large amount of C
stack space being consumed, and it was possible to overflow the stack.
For example, if you matched a 30000-byte string of "<tt class="samp">a</tt>" characters
against the expression <tt class="regexp">(a|b)+</tt>, one stack frame was consumed
per character.  Python 2.3 tried to check for stack overflow and raise
a <tt class="exception">RuntimeError</tt> exception, but certain patterns could
sidestep the checking and if you were unlucky Python could segfault.
Python 2.4's regular expression engine can match this pattern without
problems.

<P>
</LI>
<LI>A new <tt class="function">socketpair()</tt> function, returning a pair of
connected sockets, was added to the <tt class="module">socket</tt> module.
(Contributed by Dave Cole.)

<P>
</LI>
<LI>The <tt class="function">sys.exitfunc()</tt> function has been deprecated.  Code
should be using the existing <tt class="module">atexit</tt> module, which correctly
handles calling multiple exit functions.  Eventually
<tt class="function">sys.exitfunc()</tt> will become a purely internal interface,
accessed only by <tt class="module">atexit</tt>.

<P>
</LI>
<LI>The <tt class="module">tarfile</tt> module now generates GNU-format tar files
by default.  (Contributed by Lars Gustaebel.)

<P>
</LI>
<LI>The <tt class="module">threading</tt> module now has an elegantly simple way to support 
thread-local data.  The module contains a <tt class="class">local</tt> class whose
attribute values are local to different threads.

<P>
<div class="verbatim"><pre>
import threading

data = threading.local()
data.number = 42
data.url = ('www.python.org', 80)
</pre></div>

<P>
Other threads can assign and retrieve their own values for the
<tt class="member">number</tt> and <tt class="member">url</tt> attributes.  You can subclass
<tt class="class">local</tt> to initialize attributes or to add methods.
(Contributed by Jim Fulton.)

<P>
</LI>
<LI>The <tt class="module">timeit</tt> module now automatically disables periodic
  garbarge collection during the timing loop.  This change makes
  consecutive timings more comparable.  (Contributed by Raymond Hettinger.)

<P>
</LI>
<LI>The <tt class="module">weakref</tt> module now supports a wider variety of objects
   including Python functions, class instances, sets, frozensets, deques,
   arrays, files, sockets, and regular expression pattern objects.
   (Contributed by Raymond Hettinger.)

<P>
</LI>
<LI>The <tt class="module">xmlrpclib</tt> module now supports a multi-call extension for 
transmitting multiple XML-RPC calls in a single HTTP operation.
(Contributed by Brian Quinlan.)

<P>
</LI>
<LI>The <tt class="module">mpz</tt>, <tt class="module">rotor</tt>, and <tt class="module">xreadlines</tt> modules have 
been removed.

<P>
</LI>
</UL>

<P>

<H2><A NAME="SECTION0001310000000000000000">
12.1 cookielib</A>
</H2>

<P>
The <tt class="module">cookielib</tt> library supports client-side handling for HTTP
cookies, mirroring the <tt class="module">Cookie</tt> module's server-side cookie
support. Cookies are stored in cookie jars; the library transparently
stores cookies offered by the web server in the cookie jar, and
fetches the cookie from the jar when connecting to the server. As in
web browsers, policy objects control whether cookies are accepted or
not.

<P>
In order to store cookies across sessions, two implementations of
cookie jars are provided: one that stores cookies in the Netscape
format so applications can use the Mozilla or Lynx cookie files, and
one that stores cookies in the same format as the Perl libwww library.

<P>
<tt class="module">urllib2</tt> has been changed to interact with <tt class="module">cookielib</tt>:
<tt class="class">HTTPCookieProcessor</tt> manages a cookie jar that is used when
accessing URLs.

<P>
This module was contributed by John J. Lee.

<P>

<H2><A NAME="SECTION0001320000000000000000">
12.2 doctest</A>
</H2>

<P>
The <tt class="module">doctest</tt> module underwent considerable refactoring thanks
to Edward Loper and Tim Peters.  Testing can still be as simple as
running <tt class="function">doctest.testmod()</tt>, but the refactorings allow
customizing the module's operation in various ways

<P>
The new <tt class="class">DocTestFinder</tt> class extracts the tests from a given 
object's docstrings:

<P>
<div class="verbatim"><pre>
def f (x, y):
    """&gt;&gt;&gt; f(2,2)
4
&gt;&gt;&gt; f(3,2)
6
    """
    return x*y

finder = doctest.DocTestFinder()

# Get list of DocTest instances
tests = finder.find(f)
</pre></div>

<P>
The new <tt class="class">DocTestRunner</tt> class then runs individual tests and can
produce a summary of the results:

<P>
<div class="verbatim"><pre>
runner = doctest.DocTestRunner()
for t in tests:
    tried, failed = runner.run(t)
    
runner.summarize(verbose=1)
</pre></div>

<P>
The above example produces the following output:

<P>
<div class="verbatim"><pre>
1 items passed all tests:
   2 tests in f
2 tests in 1 items.
2 passed and 0 failed.
Test passed.
</pre></div>

<P>
<tt class="class">DocTestRunner</tt> uses an instance of the <tt class="class">OutputChecker</tt>
class to compare the expected output with the actual output.  This
class takes a number of different flags that customize its behaviour;
ambitious users can also write a completely new subclass of
<tt class="class">OutputChecker</tt>.

<P>
The default output checker provides a number of handy features.
For example, with the <tt class="constant">doctest.ELLIPSIS</tt> option flag,
an ellipsis ("<tt class="samp">...</tt>") in the expected output matches any substring, 
making it easier to accommodate outputs that vary in minor ways:

<P>
<div class="verbatim"><pre>
def o (n):
    """&gt;&gt;&gt; o(1)
&lt;__main__.C instance at 0x...&gt;
&gt;&gt;&gt;
"""
</pre></div>

<P>
Another special string, "<tt class="samp">&lt;BLANKLINE&gt;</tt>", matches a blank line:

<P>
<div class="verbatim"><pre>
def p (n):
    """&gt;&gt;&gt; p(1)
&lt;BLANKLINE&gt;
&gt;&gt;&gt;
"""
</pre></div>

<P>
Another new capability is producing a diff-style display of the output
by specifying the <tt class="constant">doctest.REPORT_UDIFF</tt> (unified diffs),
<tt class="constant">doctest.REPORT_CDIFF</tt> (context diffs), or
<tt class="constant">doctest.REPORT_NDIFF</tt> (delta-style) option flags.  For example:

<P>
<div class="verbatim"><pre>
def g (n):
    """&gt;&gt;&gt; g(4)
here
is
a
lengthy
&gt;&gt;&gt;"""
    L = 'here is a rather lengthy list of words'.split()
    for word in L[:n]:
        print word
</pre></div>

<P>
Running the above function's tests with
<tt class="constant">doctest.REPORT_UDIFF</tt> specified, you get the following output:

<P>
<div class="verbatim"><pre>
**********************************************************************
File ``t.py'', line 15, in g
Failed example:
    g(4)
Differences (unified diff with -expected +actual):
    @@ -2,3 +2,3 @@
     is
     a
    -lengthy
    +rather
**********************************************************************
</pre></div>

<P>

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