How to export an environment variable from command line ?

Question

Hello,
I have build a python application which run some processes(or executable or other python scripts) using subprocess.
i.e.
subprocess.call(["xyz.py"], shell=True, stdout=log_file, stderr=log_file)
Above call throws an error as "xyz.py is not recognized as an internal or external command." I added the location of xyz.py into path variable inside a batch script which I used to run before running the script.
 set PATH=D:\path of xyz:%PATH%
But As subprocess executes a script into anther child shell, This setting is not available in child shell (or sub-shell) used by python script.
How can I make this PATH setting available to sub-shell also ?

Answer 1

Rather than going into much details I have used explicit path by referring only one environment variable of the shell where application is running.
i.e.  As xyz.py will be in a specific location of my repository, I am setting path of root_dir:
      set root_dir=<path_of_root_dir>
      And then,
      subprocess.call([os.path.join(os.environ['roo_dir'], 'dir', 'xyz.py')], ...)