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diff --git a/Doc/howto/advocacy.tex b/Doc/howto/advocacy.tex deleted file mode 100644 index 9074b3f..0000000 --- a/Doc/howto/advocacy.tex +++ /dev/null @@ -1,411 +0,0 @@ - -\documentclass{howto} - -\title{Python Advocacy HOWTO} - -\release{0.03} - -\author{A.M. Kuchling} -\authoraddress{\email{amk@amk.ca}} - -\begin{document} -\maketitle - -\begin{abstract} -\noindent -It's usually difficult to get your management to accept open source -software, and Python is no exception to this rule. This document -discusses reasons to use Python, strategies for winning acceptance, -facts and arguments you can use, and cases where you \emph{shouldn't} -try to use Python. - -This document is available from the Python HOWTO page at -\url{http://www.python.org/doc/howto}. - -\end{abstract} - -\tableofcontents - -\section{Reasons to Use Python} - -There are several reasons to incorporate a scripting language into -your development process, and this section will discuss them, and why -Python has some properties that make it a particularly good choice. - - \subsection{Programmability} - -Programs are often organized in a modular fashion. Lower-level -operations are grouped together, and called by higher-level functions, -which may in turn be used as basic operations by still further upper -levels. - -For example, the lowest level might define a very low-level -set of functions for accessing a hash table. The next level might use -hash tables to store the headers of a mail message, mapping a header -name like \samp{Date} to a value such as \samp{Tue, 13 May 1997 -20:00:54 -0400}. A yet higher level may operate on message objects, -without knowing or caring that message headers are stored in a hash -table, and so forth. - -Often, the lowest levels do very simple things; they implement a data -structure such as a binary tree or hash table, or they perform some -simple computation, such as converting a date string to a number. The -higher levels then contain logic connecting these primitive -operations. Using the approach, the primitives can be seen as basic -building blocks which are then glued together to produce the complete -product. - -Why is this design approach relevant to Python? Because Python is -well suited to functioning as such a glue language. A common approach -is to write a Python module that implements the lower level -operations; for the sake of speed, the implementation might be in C, -Java, or even Fortran. Once the primitives are available to Python -programs, the logic underlying higher level operations is written in -the form of Python code. The high-level logic is then more -understandable, and easier to modify. - -John Ousterhout wrote a paper that explains this idea at greater -length, entitled ``Scripting: Higher Level Programming for the 21st -Century''. I recommend that you read this paper; see the references -for the URL. Ousterhout is the inventor of the Tcl language, and -therefore argues that Tcl should be used for this purpose; he only -briefly refers to other languages such as Python, Perl, and -Lisp/Scheme, but in reality, Ousterhout's argument applies to -scripting languages in general, since you could equally write -extensions for any of the languages mentioned above. - - \subsection{Prototyping} - -In \emph{The Mythical Man-Month}, Fredrick Brooks suggests the -following rule when planning software projects: ``Plan to throw one -away; you will anyway.'' Brooks is saying that the first attempt at a -software design often turns out to be wrong; unless the problem is -very simple or you're an extremely good designer, you'll find that new -requirements and features become apparent once development has -actually started. If these new requirements can't be cleanly -incorporated into the program's structure, you're presented with two -unpleasant choices: hammer the new features into the program somehow, -or scrap everything and write a new version of the program, taking the -new features into account from the beginning. - -Python provides you with a good environment for quickly developing an -initial prototype. That lets you get the overall program structure -and logic right, and you can fine-tune small details in the fast -development cycle that Python provides. Once you're satisfied with -the GUI interface or program output, you can translate the Python code -into C++, Fortran, Java, or some other compiled language. - -Prototyping means you have to be careful not to use too many Python -features that are hard to implement in your other language. Using -\code{eval()}, or regular expressions, or the \module{pickle} module, -means that you're going to need C or Java libraries for formula -evaluation, regular expressions, and serialization, for example. But -it's not hard to avoid such tricky code, and in the end the -translation usually isn't very difficult. The resulting code can be -rapidly debugged, because any serious logical errors will have been -removed from the prototype, leaving only more minor slip-ups in the -translation to track down. - -This strategy builds on the earlier discussion of programmability. -Using Python as glue to connect lower-level components has obvious -relevance for constructing prototype systems. In this way Python can -help you with development, even if end users never come in contact -with Python code at all. If the performance of the Python version is -adequate and corporate politics allow it, you may not need to do a -translation into C or Java, but it can still be faster to develop a -prototype and then translate it, instead of attempting to produce the -final version immediately. - -One example of this development strategy is Microsoft Merchant Server. -Version 1.0 was written in pure Python, by a company that subsequently -was purchased by Microsoft. Version 2.0 began to translate the code -into \Cpp, shipping with some \Cpp code and some Python code. Version -3.0 didn't contain any Python at all; all the code had been translated -into \Cpp. Even though the product doesn't contain a Python -interpreter, the Python language has still served a useful purpose by -speeding up development. - -This is a very common use for Python. Past conference papers have -also described this approach for developing high-level numerical -algorithms; see David M. Beazley and Peter S. Lomdahl's paper -``Feeding a Large-scale Physics Application to Python'' in the -references for a good example. If an algorithm's basic operations are -things like "Take the inverse of this 4000x4000 matrix", and are -implemented in some lower-level language, then Python has almost no -additional performance cost; the extra time required for Python to -evaluate an expression like \code{m.invert()} is dwarfed by the cost -of the actual computation. It's particularly good for applications -where seemingly endless tweaking is required to get things right. GUI -interfaces and Web sites are prime examples. - -The Python code is also shorter and faster to write (once you're -familiar with Python), so it's easier to throw it away if you decide -your approach was wrong; if you'd spent two weeks working on it -instead of just two hours, you might waste time trying to patch up -what you've got out of a natural reluctance to admit that those two -weeks were wasted. Truthfully, those two weeks haven't been wasted, -since you've learnt something about the problem and the technology -you're using to solve it, but it's human nature to view this as a -failure of some sort. - - \subsection{Simplicity and Ease of Understanding} - -Python is definitely \emph{not} a toy language that's only usable for -small tasks. The language features are general and powerful enough to -enable it to be used for many different purposes. It's useful at the -small end, for 10- or 20-line scripts, but it also scales up to larger -systems that contain thousands of lines of code. - -However, this expressiveness doesn't come at the cost of an obscure or -tricky syntax. While Python has some dark corners that can lead to -obscure code, there are relatively few such corners, and proper design -can isolate their use to only a few classes or modules. It's -certainly possible to write confusing code by using too many features -with too little concern for clarity, but most Python code can look a -lot like a slightly-formalized version of human-understandable -pseudocode. - -In \emph{The New Hacker's Dictionary}, Eric S. Raymond gives the following -definition for "compact": - -\begin{quotation} - Compact \emph{adj.} Of a design, describes the valuable property - that it can all be apprehended at once in one's head. This - generally means the thing created from the design can be used - with greater facility and fewer errors than an equivalent tool - that is not compact. Compactness does not imply triviality or - lack of power; for example, C is compact and FORTRAN is not, - but C is more powerful than FORTRAN. Designs become - non-compact through accreting features and cruft that don't - merge cleanly into the overall design scheme (thus, some fans - of Classic C maintain that ANSI C is no longer compact). -\end{quotation} - -(From \url{http://www.catb.org/~esr/jargon/html/C/compact.html}) - -In this sense of the word, Python is quite compact, because the -language has just a few ideas, which are used in lots of places. Take -namespaces, for example. Import a module with \code{import math}, and -you create a new namespace called \samp{math}. Classes are also -namespaces that share many of the properties of modules, and have a -few of their own; for example, you can create instances of a class. -Instances? They're yet another namespace. Namespaces are currently -implemented as Python dictionaries, so they have the same methods as -the standard dictionary data type: .keys() returns all the keys, and -so forth. - -This simplicity arises from Python's development history. The -language syntax derives from different sources; ABC, a relatively -obscure teaching language, is one primary influence, and Modula-3 is -another. (For more information about ABC and Modula-3, consult their -respective Web sites at \url{http://www.cwi.nl/~steven/abc/} and -\url{http://www.m3.org}.) Other features have come from C, Icon, -Algol-68, and even Perl. Python hasn't really innovated very much, -but instead has tried to keep the language small and easy to learn, -building on ideas that have been tried in other languages and found -useful. - -Simplicity is a virtue that should not be underestimated. It lets you -learn the language more quickly, and then rapidly write code, code -that often works the first time you run it. - - \subsection{Java Integration} - -If you're working with Java, Jython -(\url{http://www.jython.org/}) is definitely worth your -attention. Jython is a re-implementation of Python in Java that -compiles Python code into Java bytecodes. The resulting environment -has very tight, almost seamless, integration with Java. It's trivial -to access Java classes from Python, and you can write Python classes -that subclass Java classes. Jython can be used for prototyping Java -applications in much the same way CPython is used, and it can also be -used for test suites for Java code, or embedded in a Java application -to add scripting capabilities. - -\section{Arguments and Rebuttals} - -Let's say that you've decided upon Python as the best choice for your -application. How can you convince your management, or your fellow -developers, to use Python? This section lists some common arguments -against using Python, and provides some possible rebuttals. - -\emph{Python is freely available software that doesn't cost anything. -How good can it be?} - -Very good, indeed. These days Linux and Apache, two other pieces of -open source software, are becoming more respected as alternatives to -commercial software, but Python hasn't had all the publicity. - -Python has been around for several years, with many users and -developers. Accordingly, the interpreter has been used by many -people, and has gotten most of the bugs shaken out of it. While bugs -are still discovered at intervals, they're usually either quite -obscure (they'd have to be, for no one to have run into them before) -or they involve interfaces to external libraries. The internals of -the language itself are quite stable. - -Having the source code should be viewed as making the software -available for peer review; people can examine the code, suggest (and -implement) improvements, and track down bugs. To find out more about -the idea of open source code, along with arguments and case studies -supporting it, go to \url{http://www.opensource.org}. - -\emph{Who's going to support it?} - -Python has a sizable community of developers, and the number is still -growing. The Internet community surrounding the language is an active -one, and is worth being considered another one of Python's advantages. -Most questions posted to the comp.lang.python newsgroup are quickly -answered by someone. - -Should you need to dig into the source code, you'll find it's clear -and well-organized, so it's not very difficult to write extensions and -track down bugs yourself. If you'd prefer to pay for support, there -are companies and individuals who offer commercial support for Python. - -\emph{Who uses Python for serious work?} - -Lots of people; one interesting thing about Python is the surprising -diversity of applications that it's been used for. People are using -Python to: - -\begin{itemize} -\item Run Web sites -\item Write GUI interfaces -\item Control -number-crunching code on supercomputers -\item Make a commercial application scriptable by embedding the Python -interpreter inside it -\item Process large XML data sets -\item Build test suites for C or Java code -\end{itemize} - -Whatever your application domain is, there's probably someone who's -used Python for something similar. Yet, despite being useable for -such high-end applications, Python's still simple enough to use for -little jobs. - -See \url{http://wiki.python.org/moin/OrganizationsUsingPython} for a list of some of the -organizations that use Python. - -\emph{What are the restrictions on Python's use?} - -They're practically nonexistent. Consult the \file{Misc/COPYRIGHT} -file in the source distribution, or -\url{http://www.python.org/doc/Copyright.html} for the full language, -but it boils down to three conditions. - -\begin{itemize} - -\item You have to leave the copyright notice on the software; if you -don't include the source code in a product, you have to put the -copyright notice in the supporting documentation. - -\item Don't claim that the institutions that have developed Python -endorse your product in any way. - -\item If something goes wrong, you can't sue for damages. Practically -all software licences contain this condition. - -\end{itemize} - -Notice that you don't have to provide source code for anything that -contains Python or is built with it. Also, the Python interpreter and -accompanying documentation can be modified and redistributed in any -way you like, and you don't have to pay anyone any licensing fees at -all. - -\emph{Why should we use an obscure language like Python instead of -well-known language X?} - -I hope this HOWTO, and the documents listed in the final section, will -help convince you that Python isn't obscure, and has a healthily -growing user base. One word of advice: always present Python's -positive advantages, instead of concentrating on language X's -failings. People want to know why a solution is good, rather than why -all the other solutions are bad. So instead of attacking a competing -solution on various grounds, simply show how Python's virtues can -help. - - -\section{Useful Resources} - -\begin{definitions} - - -\term{\url{http://www.pythonology.com/success}} - -The Python Success Stories are a collection of stories from successful -users of Python, with the emphasis on business and corporate users. - -%\term{\url{http://www.fsbassociates.com/books/pythonchpt1.htm}} - -%The first chapter of \emph{Internet Programming with Python} also -%examines some of the reasons for using Python. The book is well worth -%buying, but the publishers have made the first chapter available on -%the Web. - -\term{\url{http://home.pacbell.net/ouster/scripting.html}} - -John Ousterhout's white paper on scripting is a good argument for the -utility of scripting languages, though naturally enough, he emphasizes -Tcl, the language he developed. Most of the arguments would apply to -any scripting language. - -\term{\url{http://www.python.org/workshops/1997-10/proceedings/beazley.html}} - -The authors, David M. Beazley and Peter S. Lomdahl, -describe their use of Python at Los Alamos National Laboratory. -It's another good example of how Python can help get real work done. -This quotation from the paper has been echoed by many people: - -\begin{quotation} - Originally developed as a large monolithic application for - massively parallel processing systems, we have used Python to - transform our application into a flexible, highly modular, and - extremely powerful system for performing simulation, data - analysis, and visualization. In addition, we describe how Python - has solved a number of important problems related to the - development, debugging, deployment, and maintenance of scientific - software. -\end{quotation} - -\term{\url{http://pythonjournal.cognizor.com/pyj1/Everitt-Feit_interview98-V1.html}} - -This interview with Andy Feit, discussing Infoseek's use of Python, can be -used to show that choosing Python didn't introduce any difficulties -into a company's development process, and provided some substantial benefits. - -%\term{\url{http://www.python.org/psa/Commercial.html}} - -%Robin Friedrich wrote this document on how to support Python's use in -%commercial projects. - -\term{\url{http://www.python.org/workshops/1997-10/proceedings/stein.ps}} - -For the 6th Python conference, Greg Stein presented a paper that -traced Python's adoption and usage at a startup called eShop, and -later at Microsoft. - -\term{\url{http://www.opensource.org}} - -Management may be doubtful of the reliability and usefulness of -software that wasn't written commercially. This site presents -arguments that show how open source software can have considerable -advantages over closed-source software. - -\term{\url{http://sunsite.unc.edu/LDP/HOWTO/mini/Advocacy.html}} - -The Linux Advocacy mini-HOWTO was the inspiration for this document, -and is also well worth reading for general suggestions on winning -acceptance for a new technology, such as Linux or Python. In general, -you won't make much progress by simply attacking existing systems and -complaining about their inadequacies; this often ends up looking like -unfocused whining. It's much better to point out some of the many -areas where Python is an improvement over other systems. - -\end{definitions} - -\end{document} - - |