Some time ago an old friend asked a question on the Python-IL mailing list, wondering what we thought of using Python for serious development. I think my response back then was pretty interesting, so I'm reproducing it here (edited cosmetically only). Today I would've probably put it differently, but the essence would be the same.
From: Ori Peleg Mon, 16 Apr 2007 23:17:55 -0700 Yes, you should program in Python! (or a similar agile language) :-) My main points: - Python is excellent for refactoring (beats C++ and, yes, Java too) - Don't move an inch with unit and system tests - These tests are much easier to write in Python - Compiler-checked interfaces aren't that important - After a few serious successes, Python is a very serious contender in my company. Now to our application's story: We ported a large application core to Python (original was in C++ - we wrote it too). Our motivation was maintainability - we were sure we could reduce that hulking core to a smaller and simpler creature. This really did happen, to the point that the project never went into maintenance mode - it suddenly became useful for things we didn't predict :) We got performance benefits as well (yes, we were surprised). The reasons were straightforward - we had many more options when refactoring the code, and separated a lot of logic neatly (for example extracted DB caching to a decorator - "AOP" in a language that needs a new term :-) The gains we ended up getting could have been achieved in C++, obviously, but they only became apparent after refactoring with Python. We also wrote a quick sample client/server application with Twisted, which was later modified in 2 weeks by someone different and transformed into an excellent production application, that's still working flawlessly after 6 months with no maintenance. All this with about 300 lines of simple, practically stupid, "I understand this code the first time I see it" code (actually, this is probably the reason for the quality). Now, every time someone says "client/server" people think about Python and Twisted, and even a large legacy network client is being replaced with a small Twisted client soon. How come Python is so amazing for refactoring? First, you need really good tests. I don't miss the compiler when I have really good tests. The good side is that to develop at good quality and speed you need really good tests in any language, so you're not losing anything. These tests are also so much easier to write in Python - we get more and better tests, and spend less time writing them. (Whatever language you use for the system, you should probably test in a language like Python). Once these tests are in place, refactoring in Python with a good text editor and some basic tools is so much smoother than C++ or Java, even with Eclipse's really cool 'Refactor' menu. Those actions that are trivial in Eclipse ( e.g. 'Rename Method') are a little more complicated in Python, but not by much (remember the good tests). On the other hand, anything that isn't in Eclipse's context menu is absolutely horrible to do in Java, to the point that I've met many good Java developers that don't think anything else exists at all :) In Python, I've found it to be a snap. And when you add all the more and less dynamic tools that can be put to good use, I'm one happy refactorer. Decorators, bound methods, generator expressions, and the like give me many ways to make the code simpler that aren't nearly as accessible in Java (or barely possible in C++). Why aren't interfaces that important? The reason I like interfaces is as documentation that the compiler happens to check. It's convenient, but I don't terribly miss it in the presence of (a) good documentation, and (b), you guessed it, good tests :-D I don't have much experience with zope.interface, so I don't know how easy it is to use or how much of the benefit from interfaces you get. I must say about this point that I'm comparing a full static-typing approach (e.g. Java) to a full dynamic-typing approach (e.g. Python) - give me dynamic typing any day. A hybrid statically- and dynamically-typed language like Groovy could work better, I don't have the experience to say. orip.
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