python tools invocation

There are many tools (e.g. yum/hg), which are written in python, on Linux platform. For example, on my ubuntu 13.04 box there are 45 python scripts under /usr/local/bin directory.

$ file /usr/local/bin/*|grep -ic python
45

So I should say that one can not live without them.

How are these python tools invoked?

Take tikerer as example.

$ which tinker
/usr/local/bin/tinker
$ file /usr/local/bin/tinker
/usr/local/bin/tinker: Python script, ASCII text executable

So executing tinker command will hook python package.

#!/usr/bin/python
# EASY-INSTALL-ENTRY-SCRIPT: 'Tinkerer==1.2.1','console_scripts','tinker'
__requires__ = 'Tinkerer==1.2.1'
import sys
from pkg_resources import load_entry_point

if __name__ == '__main__':
    sys.exit(
        load_entry_point('Tinkerer==1.2.1', 'console_scripts', 'tinker')()
    )

Where does this package come from? Let’s search for its location with primitive way.

$ strace -o test.txt -e open tinker -d "test"
$ grep tinker test.txt |grep -iv enoent
...
open("/usr/local/lib/python2.7/dist-packages/tinkerer/__init__.py", O_RDONLY|O_LARGEFILE) = 3
open("/usr/local/lib/python2.7/dist-packages/tinkerer/__init__.pyc", O_RDONLY|O_LARGEFILE) = 4

Ok, here is the location where relevant python package resides.

$ ls /usr/local/lib/python2.7/dist-packages/tinkerer
__init__.py   __templates  cmdline.pyc      draft.pyc  master.py   page.py   paths.py   post.py   static  utils.py   writer.py
__init__.pyc  cmdline.py   draft.py ext        master.pyc  page.pyc  paths.pyc  post.pyc  themes  utils.pyc  writer.pyc

So when one installs python package, say, with pip command, packages will be deployed under dist-packages directory. And at the same time, a wrapper script will be deployed on search path so that it invokes relevant package by making use of pkg_resources.