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<h3>Enhancements</h3>
<p>Python 2.0 comes bundled with <a NAME="idx1073751507"></a>many new features, bug fixes, and optimizations. The next list provides an appetizer for the main changes that were made, and that are about to be shown.</p>
<ul>
<LI><P>Python 2.0's source code was <A name="idx1073751508"></A>converted to ANSI C. That means that you need an ANSI C compiler in order to compile Python. Compilers that only support K&R C will not be able to compile version 2.0. Note that this isn't a big problem, as just about every C compiler these days is ANSI C compliant.</P>
</LI>
<li><p>For those of you who had problems with the size of your source code, Python 2.0 has increased the limit of expressions and files in Python source code. That limit is now <i>2**32.</i> If compared to the <i>2**16</i> that we previously had, it can be considered a good limit.</p>
</li>
<li><p>This new release also starts the porting of Python to 64-bit platforms. Currently, both Linux and Win64 are able to take care of that. Some extra effort was made especially for Intel's Itanium processor.</p>
</li>
<li><p>The support to XML was fully <a NamE="idx1073751509"></a>extended. The <tt Class="monofont">xml</Tt> package includes a renewed DOM interface and a SAX2 interface.</p>
</lI>
<LI><P>All the internals of the <tt clASS="monofont">re</Tt>
<a naME="idx1073751510"></A><A name="idx1073751511"></A><A NAme="idx1073751512"></a>module were changed. Now, the regular expression engine is located in a new module called <tt class="monofont">SRE</tt> written by Fredrik Lundh of Secret Labs AB. This was to allow Unicode strings to be used in regular expressions too. Pay attention to the <tt class="monofont">re</tT> module as it continues to be the front-end module, which internally calls the <tt ClasS="monofont">SRE</tt> module.</p>
</lI>
<li><p>Many new modules were added. (Check them out throughout the book!)</P>
</LI>
<Li><p>Many enhancements were <a nAME="idx1073751513"></A>made to IDLE. Python 2.0 is distributed with IDLE 0.6, which also contains a number of new features.</p>
</li>
<lI><P>Some methods had their syntax <A Name="idx1073751514"></a>changed for enhancement purposes, including <TT CLass="monofont">listobj.insert()</tt>, <tt class="monofont">listobj.append()</tt>, and the methods from the <tt clasS="monofont">socket</tt> module.</P>
</li>
<lI><p>Python 2.0 introduces the possibility to rename a module when importing it, for example, <tt cLass="monofont">import Module as OtherName</TT>. Note that this syntax can also be used when importing symbols from a module, for instance:</P>
<Pre>
from module import sym1 as sym2
</prE>
</LI>
<Li><p>Now, you can also redirect your print statements to a file-like object, for example, <tt CLASs="monofont">print >> fileobj, "Hello Python World"</tt>.</p>
</LI>
</UL>
<p>The following are considered to be the most important changes in this new release.</p>
<h4>Unicode Support</h4>
<p>This is a long <a name="idx1073751515"></a><a name="idx1073751516"></a>awaited feature that was finally added to the language. Unicode strings are a new sort of data type, which can handle up to 65,536 distinct characters, instead of being limited to the 256 used by the ASCII format. Python now comes with a library of <i>codecs</i> for converting between Unicode and the various character <i>encodings</I> in use. This library can be extended very easily.</p>
<h4>List Comprehension</H4>
<p>Whenever you need to <a nAme="idx1073751517"></a>compute a list (or lists) of elements in order to generate a new list, you can use this new and more efficient mechanism. It is offered for lists in order to replace the not-that-efficient method of using a <tT claSS="monofont">for</TT> loop with an <tt clASS="monofont">if</Tt> statement and a <tt cLASS="monofont">list.append()</tt> call, for example, <tt CLASs="monofont">newlist = [y+3 for y in range(15)]</tt></p>
<h4>Strings Manipulation</h4>
<p>Prior to version 2.0, you <a name="idx1073751518"></a>had to rely on the <tt class="monofont">string</Tt> module to manipulate your string objects. With this new release, the methods were pushed to the string type. Besides the methods that were inherited from the <tT claSs="monofont">string</tt> module, two new methods were also added. Note that old <tT claSS="monofont">string</TT> module was not removed from the distribution because it is still necessary for backward compatibility.</p>
<h4>Augmented Assignment</h4>
<p>Python 2.0 implements a full set of <A NAMe="idx1073751519"></a><a nAME="idx1073751520"></A>augmented assignment operators. This includes: <tt clASS="monofont">+=</Tt>, <tt class="monofont">-=</tt>, <tt class="monofont">*=</tt>, <tT clAss="monofont">/=</tT>, <tt clAss="monofont">%=</tT>, <TT Class="monofont">**=</TT>, <TT clasS="monofont">&=</TT>, <Tt claSS="monofont">|=</TT>, <tt class="monofont">^=</tt>, <tt class="monofont">⌨️ 快捷键说明
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