Question

I have an XML that contains information about environment variable to set into the shell by my python script. Here is a snippet of the XML :

<envVar name='QTDIR'>/homeqt/libs.qt4/qt4.5.1</envVar>
<envVar name='MAKE'>which make</envVar>

This part of this snippet tells my python script to set environment variables QTDIR and MAKE.

My concern is the difference how i have to set the above variables. I know that i can use os.environ to set environment variables and do something like this :

os.environ['QTDIR'] = "/homeqt/libs.qt4/qt4.5.1"

But i can’t use this to set my MAKE variable, i have to execute the command “which make” (to get the path of make executable). My goal is to use the same method/function to set every variables.

SO, i thought to do something like this:

Popen("QTDIR=/homeqt/libs.qt4/qt4.5.1 ; export QTDIR", shell=True, stdout=PIPE, stderr=PIPE)
Popen("MAKE=which make ; export MAKE", shell=True, stdout=PIPE, stderr=PIPE)

But if i do this, the variable will be set only for the subprocess, not for the current shell.

So, my question is, is there a way to do what i want? I DON’T want to analyse the XML and do something like this :

(pseudocode)

if QTDIR has normal value
    os.environ['QTDIR'] = "/homeqt/libs.qt4/qt4.5.1"
if MAKE has value to be executed
    p = Popen("which make", shell=True, stdout=PIPE, stderr=PIPE)
    stdout, stderr = p.communicate()
    os.environ['MAKE'] = stdout

Answer 1

I would make use of XML attributes.

<envVar name="MAKE" type="command">which make</envVar>
<envVar name="QTDIR" type="string">/homeqt/libs.qt4/qt4.5.1</envVar>

pseudocode depending on your xml library:

if node.attributes['type'] == 'command':
    value = os.popen(node.firstChild.text).read()
elif node.attributes['type'] == 'string':
    value = node.firstChild.text
os.environ[node.attributes['name']] = value