title: how to set environment variable in python script
body: <p>i am using SCONS Construction tool. <br>
  i am unable to use the environment variable which is initialized in python script.<br></p>
  
  <p>In My project USER can change some variables to work with the compiler.</p>
  
  <p>For that we have 2 files.</p>
  
  <ul>
  <li>Config.py</li>
  <li>Sconstruct</li>
  </ul>
  
  <p>Config.py is having all the variables which are like Include directories, CFLAGS , CPPDEFINES etc. So, Here we can set some variables. Those variables i need to use in Sconstruct file. In config.py i set a variable like below</p>
  
  <pre><code>SCONS_INC = "Include files"
  os.environ["SCONS_INC"] = SCONS_INC
  </code></pre>
  
  <p>I need to use those variables in Sconstruct File. The code is</p>
  
  <pre><code>env["CPPPATH"] = os.environ["SCONS_INC"] 
  </code></pre>
  
  <p>But I am getting an error like Undefined variable SCONS_INC.</p>
  
  <p>How to do this?</p>