python and xml

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ActiveState
Python and XML
Copyright 2001,
ActiveState
About me
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Paul Prescod, ()
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ActiveState Senior Developer
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Co-Author, XML Handbook
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Preview
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About Python
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Python SAX/DOM
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PyXML Package
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Python XSLT/XPath
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Python SOAP/XML-RPC
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XML and Zope
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What is Python?
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Python is an easy to learn, powerful
programming language.
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Efficient high-level data structures
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Simple approach to object-oriented
programming.
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Elegant syntax and dynamic typing
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Brief History of Python
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CWI, early 90s.
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Dynamic Object Oriented High Level
Language.
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More than a text processing language.
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More than a scripting language.
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Scalable and object oriented from the
beginning.
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Dynamically type checked.
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Python's business case
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Python can displace many other
languages in the organization.
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The Python interpreter is free.
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Python is legally unencumbered.
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Professional programmers find Python
more flexible than most languages.
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Amateur programmers are (often) more
comfortable than with Perl or Java.
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Usability features
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Exceptionally clear syntax.
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Provides an obvious way to do most
things.
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Small set of features combine in
powerful ways.
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Only innovative where innovation is
really necessary.
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More Usability features
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Huge amount of free code and libraries
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Interactive.
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Designed to talk to the world.
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Runs with Unix, Mac and Windows.
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Integrates with JVM (Jython) and .NET
Framework (Python.NET)
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Talks MS COM, XPCOM,
CORBA,SOAP, XML-RPC, …
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Scalability features
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Simple but powerful module system.
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Simple but powerful class system.
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Structured, standardized exceptions.
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Environments
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Unix (almost all)
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Windows (3.1, 95, NT, CE)
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Mac
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JVM
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Various legacy systems
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Extendable
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New data types in Python or C
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Modules in Python or C
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Functions in Python or C
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Python isn't picky!
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COM/CORBA
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HTML/XML/SGML
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Win API/POSIX
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You can write code that is portable or
platform-specific.
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ActiveState
Compared to Perl
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Simpler syntactically.
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More object oriented.
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Easier to extend.
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But slower regular expressions
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Compared to Java
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Java is more difficult for amateur
programmers.
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Static type checking can be
inconvenient in text processing.
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Puritanical OO can be inconvenient.
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Bottom line: Java can make simple
projects harder.
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Why not Java: political
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"100% pure Java" gets in the way.
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The Java environment punishes
interoperability. (e.g. getenv is
deprecated)

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Java is designed to have interoperability
limitations.
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Embedding Java is relatively painful.
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Jython (nee JPython)
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Compiles Python classes to Java
classes
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Embedded interpreter allows interactive
coding.
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Access to all Java classes.
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For better or worse: maintains Java's
security/platform-independence bubble.
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Jython can use Java tools
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RDF
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XPointer
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Various parsers
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Swing GUI

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Unicode
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Python Limitations
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“Ordinary Python" has 8-bit and Unicode
string types.
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Handling explicit conversions can be annoying.
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Not as fast as C++.
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Raw text searching is not as fast as Perl.
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Dynamic type checking requires more care in
testing.
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Python “Hello world"
print "Hello, World“
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Python interpreter
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Just type:
C:\> python
Python 1.5.2 (#0, Apr 13 1999, 10:51:12)
[MSC 32 bit (Intel)] on win32
Copyright 1991-1995 Stichting Mathematisch

Centrum, Amsterdam
>>> print "Hello, World"
Hello, Python
>>> print "Goodbye, World "
Goodbye, Python
>>> ^Z
C:\>
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Byte-compiling
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Python automatically bytecompiles
modules.
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Next execution does not require
compilation.
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.py files get a .pyc in the same directory
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When the .py is updated, the .pyc is
updated
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Interpreters
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DOS/Win32 (last slide)
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Unix (use ^D to exit)
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Graphical: “IDLE”, “PythonWin”

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Python variables
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Any Python variable can hold any value.
>>> width = 20
>>> height = 5 * 9
>>> width * height
900
>>> width = "really wide“
>>> width
'really wide'
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Numeric types
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int: 32 bit, e.g. "x=5"
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long: arbitrary sized, e.g. "x=2L**128"
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float: accuracy depends on platform,
e.g. "x=3.14"
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complex: real+imag., "x=5.3+3.2j"
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Sequence types:
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Strings: "abcd"
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Tuples: (1,2,"b")
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Lists: [1,"a",3]