Here's what I found in the manual:
- data of module posix: environ
A dictionary representing the string environment at the time the
interpreter was started. (Modifying this dictionary does not
affect the string environment of the interpreter.) For example,
`posix.environ['HOME']' is the pathname of your home directory,
equivalent to `getenv("HOME")' in C.
- function of module posix: system (COMMAND)
Execute the command (a string) in a subshell. This is implemented
by calling the Standard C function `system()', and has the same
limitations. Changes to `posix.environ', `sys.stdin' etc. are not
reflected in the environment of the executed command. The return
value is the exit status of the process as returned by Standard C
`system()'.
Eric