Python www python org Whats in a name

Python www. python. org

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

What is Python? • O-O rapid prototyping language • Not just a scripting language • Not just another Perl-wannabe • Extensible (add new modules) – C/C++/Fortran/whatever – Java (through JPython) • Embeddable in applications

Touchy-feely properties • Free (open source) – copyrighted but use not restricted • Mature (9 years old) • Supportive user community – & more books in the pipeline! • Elegant design, easy to learn – reads like “pseudo-code” – Suitable as first language

High-level properties • Extremely portable – Unix, Windows, Mac, Be. OS, Win/CE, DOS, OS/2, Amiga, VMS, Cray, … • Compiles to interpreted byte code – compilation is implicit and automatic • Memory mgt through ref counting – easier for C/C++ extensions • “Safe”: no core dumps

Interfaces to. . . • COM, DCOM, ODBC • Commercial databases • Java (JPython) • Many GUI libraries – platform-independent • Tk, wx. Windows, GTK – platform-specific • MFC, Mac. OS, X 11

Language properties • Everything is an object • Modules, classes, functions • Exception handling • Dynamic typing, polymorphism • Static scoping • Operator overloading • Indentation for block structure – Otherwise conventional syntax

High-level data types • Numbers: int, long, float, complex • Strings: immutable • Lists and dictionaries: containers • Other types for e. g. binary data, regular expressions, introspection • Extension modules can define new “built-in” data types

What is it used for? • rapid prototyping • web scripting • throw-away, ad hoc programming • steering scientific applications • extension language • XML processing • database applications • GUI applications

Who is using it? • LLNL, Fermilab (steering) • Alice project at CMU (3 D graphics) • Object. Domain (extend UML tool) • Infoseek (ext. language, scripting) • Industrial Light & Magic (everything) • Yahoo! (CGI in Yahoo!mail) • Digital Creations (Zope website mgt) • Red. Hat (Linux installation tools)

Compared to Perl • Easier to learn – especially for infrequent users • More readable code – improved code maintenance • Fewer “magical” side effects • More “safety” guarantees • Better Java integration • Some things slower

Compared to Java • Code 5 -10 times more concise • Dynamic typing • Much quicker development – no compilation phase – less typing • Yes, it runs slower – but development is much faster! Ditto (but more so) for C/C++

Compared to Tcl • Real datatypes, object-orientation • More differentiated syntax • Much faster (even than Tcl 8. 0) • Can use threads • Less need for C extensions – hence fewer extension conflicts • Better Java integration • Python uses Tk as de-facto GUI std

JPython • Seamless integration with Java • Separate implementation – “classic Python” called CPython here • Implements the same language • Different set of standard modules • differences in “gray areas” – e. g. some different introspection calls – different command line options, etc.

Java integration • Interactive • Compiles direct to Java bytecode • Import Java classes directly • Subclass Java classes – pass instances back to Java • Java beans integration • Can compile into Java class files – run as applet in browsers

Example function def gcd(a, b): “greatest common divisor” while a != 0: a, b = b%a, a # parallel assignment return b

Example 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