Good python software developers tend to use distutils and include a setup.py with their code. The problem I often encounter is finding out which prefix your software has been installed in from within the python code. This might be necessary if you want to interact with some data that you’ve installed into: $prefix/share/projectname/ Here are the various steps:
1) Distutils:
NAME='someproject'
distutils.core.setup(
name=NAME,
version='0.1',
author='James Shubin',
author_email='purpleidea@gmail.com',
url='https://ttboj.wordpress.com/',
description='This is an example project',
# http://pypi.python.org/pypi?%3Aaction=list_classifiers
classifiers=[
'Environment :: Console',
'Intended Audience :: System Administrators',
'License :: OSI Approved :: GNU Affero General Public License v3',
'Operating System :: POSIX :: Linux',
'Programming Language :: Python',
'Topic :: Utilities',
],
packages=[NAME],
package_dir={NAME: 'src'},
data_files=[
('share/%s' % NAME, ['README']),
('share/%s' % NAME, ['images/something.png']),
],
scripts=['somebin'],
)
2) Install:
python setup.py install --prefix=~/testprefix/
Note: If you don’t specify a prefix, then this will get installed into your system prefix.
3) Run:
cd ~/testprefix/ # the prefix you chose above
PYTHONPATH=lib/python2.7/site-packages/ ./bin/somebin
Note: If you didn’t specify a prefix above, then you don’t need to set the PYTHONPATH variable, and also, the executable will already be in your default $PATH
4) Prefix:
I have written a small python module which I include in all of my python software. It will returns the projects installed prefix when run. I usually use it like so:
print 'something.png is located at: %s' % os.path.join(prefix.prefix(), 'share', NAME, 'images', 'something.png')
5) Code:
Here is the code for prefix.py. I put this file under my projectname/src/ directory.
#!/usr/bin/python
# -*- coding: utf-8 -*-
"""Find the prefix of the current installation, and other useful variables.
Finding the prefix that your program has been installed in can be non-trivial.
This simplifies the process by allowing you to import <packagename>.prefix and
get instant access to the path prefix by calling the function named: prefix().
If you'd like to join this prefix onto a given path, pass it as the first arg.
Example: if [ `./prefix.py` ]; then echo yes; else echo no; fi
Example: x=`./prefix.py`; echo 'prefix: '$x
"""
# Copyright (C) 2010-2012 James Shubin
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
__all__ = ('prefix', 'name')
#DEBUG = False
import os
import sys
def prefix(join=None):
"""Returns the prefix that this code was installed into."""
# constants for this execution
path = os.path.abspath(__file__)
#if DEBUG: print 'path: %s' % path
name = os.path.basename(os.path.dirname(path))
#if DEBUG: print 'name: %s' % name
this = os.path.basename(path)
#if DEBUG: print 'this: %s' % this
# rule set
rules = [
# to match: /usr/lib/python2.5/site-packages/project/prefix.py
# or: /usr/local/lib/python2.6/dist-packages/project/prefix.py
lambda x: x == 'lib',
lambda x: x == ('python%s' % sys.version[:3]),
lambda x: x in ['site-packages', 'dist-packages'],
lambda x: x == name, # 'project'
lambda x: x == this, # 'prefix.py'
]
# matching engine
while len(rules) > 0:
(path, token) = os.path.split(path)
#if DEBUG: print 'path: %s, token: %s' % (path, token)
rule = rules.pop()
if not rule(token):
#if DEBUG: print 'rule failed'
return False
# usually returns: /usr/ or /usr/local/ (but without slash postfix)
if join is None:
return path
else:
return os.path.join(path, join) # add on join if it exists!
def name(pop=[], suffix=None):
"""Returns the name of this particular project. If pop is a list
containing more than one element, name() will remove those items
from the path tail before deciding on the project name. If there
is an element which does not exist in the path tail, then raise.
If a suffix is specified, then it is removed if found at end."""
path = os.path.dirname(os.path.abspath(__file__))
if isinstance(pop, str): pop = [pop] # force single strings to list
while len(pop) > 0:
(path, tail) = os.path.split(path)
if pop.pop() != tail:
#if DEBUG: print 'tail: %s' % tail
raise ValueError('Element doesnʼt match path tail.')
path = os.path.basename(path)
if suffix is not None and path.endswith(suffix):
path = path[0:-len(suffix)]
return path
if __name__ == '__main__':
join = None
if len(sys.argv) > 1:
join = ' '.join(sys.argv[1:])
result = prefix(join)
if result:
print result
else:
sys.exit(1)
Why this sort of thing isn’t built into python boggles my mind, so if for some reason you have a better solution, please let me know. Also, don’t be fooled by the red herring that is: sys.prefix
Happy hacking,
James
