I'm pretty used to referencing variables inside print blocks in Perl. I'm not at all comfortable with Python. I have a block of code that I want to change the 'onhg' to come out of a config file. So I set up a scratch directory and make a bare bones implementation:

[th199096@jhereg etc]> ls -laiR ~/scratch/
/home/th199096/scratch/:
total 42
       749 drwxr-xr-x   3 th199096 staff          4 Oct  6 16:36 .
         3 drwxr-xr-x  39 th199096 staff         55 Oct  6 16:35 ..
       752 drwxr-xr-x   2 th199096 staff          6 Oct  6 16:42 etc
       750 -rwxr-xr-x   1 th199096 staff       1297 Oct  6 16:42 updateoso.py

/home/th199096/scratch/etc:
total 25
       752 drwxr-xr-x   2 th199096 staff          6 Oct  6 16:42 .
       749 drwxr-xr-x   3 th199096 staff          4 Oct  6 16:36 ..
       753 -rw-r--r--   1 th199096 staff       1052 Oct  6 16:40 __init__.py
       754 -rw-r--r--   1 th199096 staff        243 Oct  6 16:41 __init__.pyc
       751 -rwxr-xr-x   1 th199096 staff         94 Oct  6 16:42 config.py
       756 -rw-r--r--   1 th199096 staff        257 Oct  6 16:42 config.pyc

Where the config file simply has:

GATE_USER = "onhg"
GATE_GROUP = "gk"

OSOREPO = "ssh://hg.opensolaris.org/hg/onnv/onnv-gate"

And the updateoso has:

import os, pwd, subprocess, sys

from mercurial import hg, repo
from mercurial.node import hex

sys.path.insert(1,
    os.path.realpath(os.path.join(os.path.dirname(__file__), "..")))
from etc import config

__USAGE = """
updateoso.py [-n] <-R repo root>
    -n: dry run, no email sent (displayed on stdout)
    -R: root dir of repo (where .hg is)

Attempt to send changes to 
%s

This script must be run as user "onhg".
You should set up RBAC and use pfexec(1).
""" % (config.OSOREPO)
__USAGE = __USAGE.strip()

print >> sys.stderr, __USAGE

Well, in isolation, I can already see what I am going to have to do. All I need to do is replace the 'ohng' with a %s and add a second argument:

[th199096@jhereg ~/scratch]> diff updateoso.py updateoso.py.first 
39c39
< This script must be run as user "%s".
---
> This script must be run as user "ohng".
41c41
< """ % (config.OSOREPO, config.GATE_USER)
---
> """ % (config.OSOREPO)

And we get:

[th199096@jhereg ~/scratch]> ./updateoso.py
updateoso.py [-n] <-R repo root>
    -n: dry run, no email sent (displayed on stdout)
    -R: root dir of repo (where .hg is)

Attempt to send changes to 
ssh://hg.opensolaris.org/hg/onnv/onnv-gate

This script must be run as user "onhg".
You should set up RBAC and use pfexec(1).

I ought to be able to test this inside the interactive shell:

[th199096@jhereg ~/scratch]> python
Python 2.4.4 (#1, Aug 25 2008, 03:30:42) [C] on sunos5
Type "help", "copyright", "credits" or "license" for more information.
>>> import updateoso
updateoso.py [-n] <-R repo root>
    -n: dry run, no email sent (displayed on stdout)
    -R: root dir of repo (where .hg is)

Attempt to send changes to 
ssh://hg.opensolaris.org/hg/onnv/onnv-gate

This script must be run as user "onhg".
You should set up RBAC and use pfexec(1).
>>> config.GATE_USER = "duke"
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name 'config' is not defined

Okay, I should have known that wasn't going to work. It would probably work in the code (we'll see later), but for now this will work:

>>> updateoso.config.GATE_USER = "duke"
>>> reload(updateoso)
updateoso.py [-n] <-R repo root>
    -n: dry run, no email sent (displayed on stdout)
    -R: root dir of repo (where .hg is)

Attempt to send changes to 
ssh://hg.opensolaris.org/hg/onnv/onnv-gate

This script must be run as user "duke".
You should set up RBAC and use pfexec(1).
<module 'updateoso' from 'updateoso.pyc'>

To be honest, I knew the reference would work, but I expected it to be reset. In retrospect, I can see that I reloaded updateoso and etc/config. Just something to get used to. I could force it to 'reset' via:

>>> reload(etc/config)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
NameError: name 'etc' is not defined
>>> from etc reload(config)
  File "<stdin>", line 1
    from etc reload(config)
                  ^
SyntaxError: invalid syntax
>>> reload(updateoso.config)
<module 'etc.config' from 'etc/config.pyc'>
>>> reload(updateoso)
updateoso.py [-n] <-R repo root>
    -n: dry run, no email sent (displayed on stdout)
    -R: root dir of repo (where .hg is)

Attempt to send changes to 
ssh://hg.opensolaris.org/hg/onnv/onnv-gate

This script must be run as user "onhg".
You should set up RBAC and use pfexec(1).
<module 'updateoso' from 'updateoso.pyc'>

Took me a bit to figure out the syntax.

Okay, can I see the change from the script:

[th199096@jhereg ~/scratch]> diff updateoso.py updateoso.py.second 
45,48d44
< 
< config.GATE_USER = "gark"
< print >> sys.stderr, __USAGE
< 

I don't expect this to work. And it doesn't.

This script must be run as user "onhg".
...
This script must be run as user "onhg".

How about a test driver script?

[th199096@jhereg ~/scratch]> more test.py 
import updateoso

print "Now change the user"

updateoso.config.GATE_USER = "nark"

reload(updateoso)

And that works:

This script must be run as user "onhg".
...
Now change the user
...
This script must be run as user "nark".