So…. you’ve been developing serious Java applications for quite a few years now, and while it was fun and enjoyable to discover the best practices, the misc. tools, how the messy fragmented ecosystem of frameworks and libraries hardly wonderfully integrates thanks to amazing JEE-whatever integration stacks (Spring, no pun intended), you now feel that the platform has become pretty much boring, and you want to try something else.. Of course, you still love Java (it pays more) and think it is still the best way to write serious applications (currently waiting for Scala to get decent IDE support ?). You do not want to hear about this over-hyped language that is supposedly perfect because you simply don’t like languages that use half of the keyboard’s non-letter keys as metacharacters. But you definitely want to hack a little bit using some dynamic language (maybe because you feel like an idiot when these dynamic-language lovers tell you they get a 10x productivity boost by using XXX instead of Java – replace XXX by whatever trendy, over-hyped popular language of the moment). Anyways.. for some reason, your choice is Python (if not, then the rest of this post is of no interest to you). You have read a book or two online, and since you’re not an idiot, you already know how to code basic stuff (still need to lookup some stuff here and there, not sure of what is idiomatic yet, but you have definitely grasped the basic concepts). However, you feel a little bit alone in this new world, wondering what the best practices are, which tools are generally used.. etc. And nobody on the internet really helps you because when it comes to giving technological advice, people are either of the “mine is bigger than yours” type, or the “everything depends on your needs/preference/[…]” BS. So, here are a few things I learned while developping pymager, a RESTful image conversion/rescaling service (hopefully, it will help you to find your way):
- The equivalent of jars is eggs.
- The equivalent of maven dependency resolution/download system is easy_install or the newer pip that is even better.
- The equivalent of ibiblio main repository is Pypi.
- the equivalent of maven is either distutils or setuptools. distutils is the default tool shipped with python, and setuptools is an alternative, that is simply superior. This is what runs your unit tests and creates source/egg packages for you.
- Installing dependencies can be done using several ways : using easy_install / pip (pollutes your system), using your system package manager (e.g. debian/ubuntu apt-get : super-clean, but does not install the most up to date packages), and easy_install / pip inside a virtualenv sandbox . See Tools for the modern Python hacker for some help regarding virtualenv.
- There are mainly 2 decent stacks for creating web applications : Django and TurboGears 2. Django is for people who like monolithic frameworks that reinvent the wheel, and TurboGears 2.0 is for people who favor integrating best-of-the-breed components. (TG2 gives you this integration for free, so you can see it as an equivalent of Spring ROO ).
- The equivalent of Hibernate is SQLAlchemy. In addition to what hibernate gives you, SQLAlchemy provides you with some lower-level utilities (such as SQL manipulation, DB-agnostic way to create a connection, ..). However, the transaction management is clearly inferior to what you get with Spring/Hibernate and their ThreadLocal implementation is just a hack that is clearly not suited to anything else than using from a web framework. If you need to do anything more serious, you will need to reinvent the wheel (See pymager’s reimplementation of ThreadLocal’s transaction management ).
- There are a dozen ways to expose a python webapp including nasty CGI-related techniques. All of them are either hacks or legacy stuff except the newer WSGI approach. Most websites use fancy names for describing what WSGi does, but it is mostly an equivalent of the servlet API.
- Cherrypy is a wonderful embedded web server that supports WSGi (and that can be used as a WSGi application itself behind apache, pretty much like tomcat can serve applications behind mod_jk). It used to be the one shipped with TurboGears, but they switched to Paste for some political reasons. (that was necessary for the merge with pylons)
- Naming conventions are a joke in python, as nobody seems to follow the same rules. Even some modules in the python standard library (e.g.: unittest module) seem to adopt different conventions than what looks like the python coding standard. I guess that too many ex-java developers program in python without being able to let away their java naming conventions..
- As a Java developer, there is some OO purity that you will need to forget about. It seems to be the “python way” to use module-wide variables, and you feel like you are fighting the platform / frameworks if you insist on applying your IoC best practices…
- nose is the way to go for running tests. (it integrates well with setuptools)
- there is no really manipulable classpath, and the default python mechanisms for discovering / handling files/data the equivalent of the classpath is pkg_resources. (an additional reason to use setuptools)
