A testimonial

(Converted to HTML by Guido van Rossum.)

Newsgroups: comp.lang.perl,comp.lang.tcl
From: lutz@xvt.com (Mark Lutz)
Subject: Python (was Re: Has anyone done a tk addition to perl?)
Organization: XVT Software Inc.
Date: Thu, 14 Oct 1993 17:10:37 GMT
X-Disclaimer: The views expressed in this message are those of an individual at XVT Software Inc., and do not necessarily reflect those of the company.

I've gotten a number of requests for information about Python, since my post here earlier this week. Since this appears to be of general interest, and since there's no python news group yet, I'm posting a description here. I'm not the best authority on the language, but here's my take on it.

[TCL/Perl zealots: this is informational only; I'm not trying to 'convert' anybody, and don't have time for a language war :-) There is a paper comparing TCL/Perl/Python/Emacs-Lisp, which is referenced in the comp.lang.misc faq, I beleive.]

What is Python?...

Python is a relatively new very-high-level language developed in Amsterdam. Python is a simple, procedural language, with features taken from ABC, Icon, Modula-3, and C/C++.

Its central goal is to provide the best of both worlds: the dynamic nature of scripting languages like Perl/TCL/REXX, but also support for general programming found in the more traditional languages like Icon, C, Modula,...

As such, it can function as a scripting/extension language, as a rapid prototyping language, and as a serious software development language. Python is suitable for fast development of large programs, but also does well at throw-away shell coding.

Python resembles other scripting languages a number of ways:

• dynamic, interpretive, interactive nature
• no explicit compile or link steps needed
• no type declarations (it's dynamically typed)
• high-level operators ('in', concatenation, etc)
• automatic memory allocation/deallocation (no 'pointers')
• high level objects: lists, tuples, strings, associative arrays
• programs can construct and execute program code using strings
• very fast edit/compile/run cycle; no static linking
• well-defined interface to and from C functions and data
• well-defined ways to add C modules to the system and language

• it's object-oriented; it has a simplified subset of C++'s 'class' facility, made more useful by python's dynamic typing; the language is object-oriented from the ground up (rather than being an add-on, as in C++)
• it supports modules (imported packages, as in Modula-3); modules replace C's 'include' files and linking, and allow for multiple-module systems, code sharing, etc.;
• it has a good exception handling system (a 'try' statement, and a 'raise' statement, with user-defined exceptions);
• it's orthogonal; everything is a first-class object in language (functions, modules, classes, class instance methods...) and can be assigned/passed and used generically;
• it's fairly run-time secure; it does many run-time checks like index-out-of-bounds, etc., that C usually doesn't;
• it has general data structuring support; Python lists are heterogeneous, variable length, nestable, support slicing, concatenation, etc., and come into existance and are reclaimed automatically; strings and dictionaries are similarly general;
• it's got a symbolic debugger and profiler (written in python, of course..), and an interactive command-line interface; as in Lisp, you can enter code and test functions in isolation, from the interactive command line (even linked C functions);
• it has a large library of built-in modules; it has support for sockets, regular expressions, posix bindings, etc.
• it supports dynamic loading of C modules on many platforms;
• it has a _readable_ syntax; python code looks like normal programming languages; tcl and perl can be very unreadable (IMHO; what was that joke about Perl looking the same after rot13..); python's syntax is simple, and statement based;

Of course, Python isn't perfect, but it's a good compromise betweem scripting languages and traditional ones, and so is widely applicable. 'Perfect' languages aren't always useful for real-world tasks (Prolog, for example), and languages at either extreme are not useful in the other domain (C is poor for shell coding and prototyping, and awk is useless for large systems design; Python does both well).

For example, I've used Python successfully for a 4K line expert system shell project; it would have been at least twice as large in C, and would have been very difficult in TCL or Perl.

Python uses an indentation-based syntax which may seem unusual at first to C coders, but after using it I have found it to be _very_ handy, since there's less to type. [I now forget to type '}' in my C code, and am busy calculating how much time I wasted typing all those '}', 'END', etc., just to pander to 'brain-dead' C/Pascal compilers :-)].

Python's currently at release 0.9.9. It seems suprisingly stable. The first 'official' 1.0 release is due out by the end of this year. Python runs on most popular machines/systems (mac, dos, unix, etc.) It's public domain and distributable, and can be had via ftp. The distribution includes examples, tutorials, and documentation. The latest ftp address I have (I got it on a cd-rom): [see the Python web site.]

There's a python mailing list maintained by the language's creator. Mail 'python-list-request@cwi.nl' to get on it.

Mark Lutz
lutz@xvt.com