Python Guido van Rossum Sung-Jin Hong SPARCS

Slide 2©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong What’s in a name? Snake logos and mascot notwithstanding, it’s named after Monty Python’s Flying Circus Humor-impaired can safely ignore the spam references :-) Nobody expects the Spanish inquisition

Slide 3©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong What is Python? O-O rapid prototyping language Not just a scripting language Not just another Perl Easy to learn, read, use Extensible (add new modules) –C/C++/Fortran/whatever –Java (through Jython) Embeddable in applications

Slide 4©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Touchy-feely properties Open Source (OSI Certified) –copyrighted but use not restricted –no "viral" license –owned by independent non-profit, PSF Mature (13 years old) Supportive user community –plenty of good books, too Simple design, easy to learn –reads like “pseudo-code” –Suitable as first language –Suitable as last language :-)

Slide 5©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong High-level properties Extremely portable –Unix/Linux, Windows, Mac, PalmOS, WindowsCE, RiscOS, VxWorks, QNX, OS/2, OS/390, AS/400, PlayStation, Sharp Zaurus, BeOS, VMS… Compiles to interpreted byte code –compilation is implicit and automatic Memory management automatic –reference counting for most situations –GC added for cycle detection “Safe”: no core dumps due to your bugs

Slide 6©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong What is it used for? rapid prototyping web programming (client and server side) ad hoc programming ("scripting") steering scientific applications extension language XML processing database applications GUI applications education

Slide 7©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Who is using it? Google (various projects) NASA (several projects) NYSE (one of only three languages "on the floor") Industrial Light & Magic (everything) Yahoo! (Yahoo mail & groups) RealNetworks (function and load testing) RedHat (Linux installation tools) LLNL, Fermilab (steering scientific applications) Zope Corporation (content management) ObjectDomain (embedded Jython in UML tool) Alice project at CMU (accessible 3D graphics) More success stories at

Slide 8©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Language properties Everything is an object Packages, modules, classes, functions Exception handling Dynamic typing, polymorphism Static scoping Operator overloading Indentation for block structure –Otherwise conventional syntax

Slide 9©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong High-level data types Numbers: int, long, float, complex Strings, Unicode: immutable Lists and dictionaries: containers Other types for e.g. binary data, regular expressions, introspection Extension modules can define new “built-in” data types

Slide 10©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Interfaces to... XML –DOM, expat –XMLRPC, SOAP, Web Services Relational databases –MySQL, PostgreSQL, Oracle, ODBC, Sybase, Informix Java (via Jython) Objective C COM, DCOM (.NET too) Many GUI libraries –cross-platform Tk, wxWindows, GTK, Qt –platform-specific MFC, Mac (classic, Cocoa), X11

Slide 11©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Compared to Perl Easier to learn –very important for infrequent users More readable code More maintainable code Fewer “magical” side effects More “safety” guarantees Better Java integration

Slide 12©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Compared to Java Code up to 5 times shorter –and more readable Dynamic typing Multiple inheritance, operator overloading Quicker development –no compilation phase –less typing Yes, it may run a bit slower –but development is much faster –and Python uses less memory (studies show) Similar (but more so) for C/C++

Slide 13©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Jython Seamless integration with Java Separate implementation Implements the same language Different set of standard modules differences in “gray areas” –e.g. some different introspection calls –different command line options, etc.

Slide 14©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Jython's Java integration Interactive Compiles directly to Java bytecode Import Java classes directly Subclass Java classes –pass instances back to Java Java beans integration Can compile into Java class files

Slide 15©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong IronPython Seamless integration with.NET framework Separate implementation –Python interpreter in.NET CLI Implements the same language Same set of standard modules Developed by Microsoft Easy integration with C#, VB, etc..

Slide 16©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong PyPy Python implemented in Python For studying

Slide 17©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Example function def gcd(a, b): "greatest common divisor" while a != 0: a, b = b%a, a # parallel assignment return b

Slide 18©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong Example class class Stack: "A well-known data structure" # doc string def __init__(self): # constructor self.items = [] def push(self, x): self.items.append(x) # the sky is the limit def pop(self): x = self.items[-1] # what happens if it’s empty? del self.items[-1] return x def empty(self): return len(self.items) == 0

Slide 19©2001, 2002 Guido-van-Rossum2006 Sung-Jin Hong References and plugs References: – - Python home site documentation, downloads, community, PSF – - success stories – - interview with GvR – - Zope community site – - Zope corporate site Python Conferences (see –PyCon DC March Washington, DC on-line registration ends today ($200) –Python UK April 2-3 Oxford, England –EuroPython June Charleroi, Belgium –Python11 at OSCON July 7-11 Portland, OR