Rusty Razor Blade » python

New Project: Jester

jon — Fri, 03 Feb 2012 19:48:16 +0000

I’ve started a new open source project called Jester. Jester is a rules engine for points and badges, also known as Gamification.

Jester is written in Python, using Redis for storage.

I’ve created a tiny Domain Specific Language for defining rules using the pyparsing library.

A couple examples of rules:

create rule on game_play award 5 points
create rule on game_play award badge game_addict when game_play occurs 5 times in 1 day

This project is in the very early stages and is not yet functional as of this posting. However, I expect to have a rough working version of it up by the end of next week.

Jester on github

Installing MySQLdb on MacOS Lion

jon — Thu, 10 Nov 2011 06:58:01 +0000

I ran into an issue installing the MySQLdb module.

>>> import MySQLdb
/Library/Python/2.7/site-packages/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg/_mysql.py:3: UserWarning: Module _mysql was already imported from /Library/Python/2.7/site-packages/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg/_mysql.pyc, but /Users/jhaddad/Downloads/MySQL-python-1.2.3 is being added to sys.path
Traceback (most recent call last):
File ““, line 1, in
File “MySQLdb/__init__.py”, line 19, in
import _mysql
File “build/bdist.macosx-10.7-intel/egg/_mysql.py”, line 7, in
File “build/bdist.macosx-10.7-intel/egg/_mysql.py”, line 6, in __bootstrap__
ImportError: dlopen(/var/root/.python-eggs/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp/_mysql.so, 2): Library not loaded: libmysqlclient.18.dylib
Referenced from: /var/root/.python-eggs/MySQL_python-1.2.3-py2.7-macosx-10.7-intel.egg-tmp/_mysql.so
Reason: image not found

I fixed it by doing the following:

sudo ln -s /usr/local/mysql/lib/libmysqlclient.18.dylib /usr/lib/libmysqlclient.18.dylib

sudo ln -s /usr/local/mysql/lib /usr/local/mysql/lib/mysql

I’m not sure if it matters, but I’ve got MySQL 5.5 installed.

Found the answer here – but it wasn’t the top voted one. If this is useful, vote Chris up.

http://stackoverflow.com/questions/4730787/python-import-mysqldb-error-mac-10-6

Install issue pymongo on OSX (setuptools out of date)

jon — Fri, 22 Apr 2011 23:33:01 +0000

easy_install on the mac has some weird hardcoding issue where it uses a specific version of setuptools. You can read a really good explanation by Andreas Jacobsen here.

The fix is to use python to call easy_install instead of using the Apple provided one.

sudo python -m easy_install pymongo

Another Attempt At Python

jon — Fri, 22 Apr 2011 20:32:13 +0000

I tried Python out a while ago, but stopped trying it to learn it after some major frustrations. Maybe I didn’t dig deep enough into it. I found the documentation hard to read, and the module layout seemed a little random at times. For some reason I found executing an external process and getting the results to be a little convoluted. (Since then I’ve learned to use popen(..).communicate())

I ended up messing with other languages to try to find one that suits my tastes, like Erlang and D. I read through 7 languages in 7 weeks, and not really getting a lot out of it. I didn’t fall in love with ruby at all and I’m not going to actually use Prolog anywhere, even if I thought it was pretty cool. I never liked Java, and I wasn’t impressed with Scala.

The closest I’ve gotten to a new favorite is Erlang. I’ve written a whole slew of posts about it. I like Erlang’s process management, message passing, and the OTP libraries. I like talking about it with people and I advocate it’s advantages. But when it comes time to write it, I find it to be clumsy and awkward, the syntax annoying and the external libraries painful. For instance, trying to work with a MongoDB database just doesn’t feel right. My mind likes OO code, and I’m done fighting it. So time to try something else.

I thought D was really interesting, but unfortunately it looks like no one is using it. It’s not even clear which compiler I should use, and the installation instructions were incorrect when I tried to set it up. Not a big selling point, and I gave that up pretty quickly.

So, another look at Python. Working with threads in Python kind of sucks. If you have multiple cores, it doesn’t really care. That’s unfortunate. However, after reading through convos in IRC (#python on freenode) I’ve found a few things that are making me give it another look. For instance, the multiprocessing module seems to address my gripes about processes / threads. Yes we’re creating OS processes, but I really only need a few (5, 10 maybe?) so having a few running shouldn’t be a problem, and the OS will take care of loading up my cores for me. It’s got great support for MongoDB (my shiny new toy) and I like it’s clean syntax. I think tornado looks really cool and I’m excited to write a stand alone server that I can bundle instead of requiring nginx configs and complicated setups.

So… I’m back writing Python. We’ll see how it goes.

Python Module Docs

jon — Wed, 28 Apr 2010 00:12:05 +0000

I’ve been trying to get into Python in my spare time, since it’s got such a huge volume of modules and looks like it should be easy to be ripping it up in no time. But of course, I have my complaints.

Fortunately I don’t need to write a long blog post, this guy did it for me. It’s kind of alarming this post is from 2 years ago and the docs are still a major problem.

I’ve got a gripe with every language (who doesn’t?) but this is really killing me. Such great potential.

PyDev Tutorial

jon — Fri, 20 Nov 2009 20:54:23 +0000

I found a good tutorial on IBM on doing Python development with Eclipse. It might be a little out of date, but I think only the screens got moved around a little bit. It includes details on how to use ant, which I’ve recently started using with cruise control and PHP, so I’m becoming a fan.

I did run into an issue where I’d get the error ‘Variable references empty selection: ${project_loc}”, but a quick google brought me to a solution here.

I only had PDT installed, which doesn’t come with the Ant tools. You just need to install the Eclipse Java Development Tools. Found that tip on Stack Overflow.

Otherwise, a great tutorial on how to get working with Eclipse and Python.

PyTables user’s guide

jon — Fri, 02 Oct 2009 03:01:06 +0000

I finally found the manual for PyTables. In case anyone else is as blind as I am, I’m linking to it here.

Installing NumPy on MacOS X Snow Leopard

jon — Tue, 22 Sep 2009 19:24:08 +0000

NumPy is a requirement to work with PyTables. This is the second step in the install process, after getting HDF5 set up.

These instructions are based on the ones found on the NumPy site, but I’m summarizing things for my own use later on.

First, you’ll need to install the Fortran compiler for OSX (gFortran). Fortunately there’s a Fortran universal binary installer.

Next, get the NumPy source. You can find it on Sourceforge.

Now, build with gFortran.

python setup.py build –fcompiler=gnu95
python setup.py install

Enjoy!

Issues Compiling HDf5 1.8.3 on MacOS X Snow Leopard

jon — Mon, 21 Sep 2009 19:01:03 +0000

I’m trying to evaluate pytables as a replacement for very large Python dictionaries, but having some issues getting HDF5 installed on my Mac (OS X Snow Leopard).

I’ve been getting this error:

configure: error: C compiler cannot create executables

I haven’t been able to figure out what’s wrong yet – anyone have any ideas? I’ve got XCode Tools installed, I’ve compiled Apache, PHP and Memcached without issue (prior to Snow Leopard Update).

Help, anyone?

Edit: I just found a post in the Apple discussion boards about this being a Snow Leopard specific issue. The suggestion is to install XCode off the Snow Leopard disc. I’ve reinstalled XCode, and now it successfully runs the configure command.

Mutable class instance variables in Python act like they’re static

jon — Thu, 29 May 2008 07:45:39 +0000

There’s a weird behavior in Python when dealing with Mutable types such as dictionaries, that when you modify a variable defined as a class attribute, you’re actually modifying a shared dictionary amongst all the classes. This seemed weird to me. You can read the lovely discussion about it, if you want. Or, just follow my code for a demo on how to deal with the issue. I just started Python on Monday night, so please overlook my n00bness.

## the first test will use an int, which is immutable.
class test1:
	i = 0
	def add(self):
		self.i = self.i + 1

t = test1()
t.add()
t2 = test1()
t2.add()
t3 = test1()
t3.add()

## this will output 1, cool
print t3.i

## Lets try it again with a dictionary - which is a mutable type
class test2:
	i = {} ## lets use a dictionary
	def add(self, str):
		self.i[str] = 1;

t = test2()
t.add('hi');
t.add('steve');
print t.i
# Will print the expected:
# {'steve': 1, 'hi': 1}

t2 = test2()
t2.add('bacon')
print t2.i

# But this prints:
# {'steve': 1, 'hi': 1, 'bacon': 1}
# Unexpected, in most languages

## it's necessary to define test2 in the following manner to avoid this weirdness

class test2:
	def __init__(self):
		self.i = {}
	def add(self, str):
		self.i[str] = 1;

t = test2()
t.add('hi');
t.add('steve');
print t.i
# Will print the expected:
# {'steve': 1, 'hi': 1}

t2 = test2()
t2.add('bacon')
print t2.i		

# Will now print the expected:
# {'bacon': 1}

Reading the link above is a good idea if you’re interested to know why something works the way it does.