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PythonGuido van Rossum

director of PythonLabs at Zope Corporation

mailto:guido@python.org

http://www.python.org

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Slide 2 2001, 2002 Guido van Rossum

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Slide 3 2001, 2002 Guido van Rossum

Whats in a name?

Snake logos and mascot notwithstanding,its named after Monty Pythons FlyingCircus

Humor-impaired can safely ignore thespam references :-)

Nobody expects the Spanish inquisition

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Slide 4 2001, 2002 Guido van Rossum

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

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Slide 5 2001, 2002 Guido van Rossum

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 :-)

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Slide 6 2001, 2002 Guido van Rossum

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

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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

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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 www.pythonology.com

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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

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High-level data types

Numbers: int, long, float, complex Strings, Unicode: immutable

Lists and dictionaries: containers

Other types for e.g. binary data, regularexpressions, introspection

Extension modules can define new built-in data types

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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

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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

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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++

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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.

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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

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Example function

def gcd(a, b):"greatest common divisor"

while a != 0:

a, b = b%a, a # parallel assignment

return b

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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 its empty?

del self.items[-1]

return x

def empty(self):

return len(self.items) == 0

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References and plugs

References: www.python.org - Python home site

documentation, downloads, community, PSF

www.pythonology.org - success stories

www.artima.com/intv - interview with GvR

www.zope.org - Zope community site

www.zope.com - Zope corporate site

Python Conferences (see www.python.org): PyCon DC March 26-28 Washington, DC

on-line registration ends today ($200) Python UK April 2-3 Oxford, England EuroPython June 25-27 Charleroi, Belgium Python11 at OSCON July 7-11 Portland, OR