python 3.4 multiprocessing-为不同的进程更改ld_library_path

Question

I'm using python multiprocessing module to call a python function in separate process, and I want a different value for the environment variable $LD_LIBRARY_PATH for this processes. Specifically, I need to append a string to the existing value before the process refers to it. An example code is shown below:

import os
from multiprocessing import Process
import sys

orig_env = os.environ['LD_LIBRARY_PATH']

def startProc_A():
   a_env = orig_env + 'path/1'
   os.environ['LD_LIBRARY_PATH'] = a_env
   print(os.environ['LD_LIBRARY_PATH'])
   sys.path.append('path/1')
   new_proc = Process(target = func_A, args=(0,))
   new_proc.start()

def func_A():
   import module_A

In the print statement, I can see that os.environ['LD_LIBRARY_PATH'] has been correctly updated, however, my process is still referring to the value that it had when python was started , meaning that module_A is still referring to the old LD_LIBRARY_PATH

Is there a way to update this value dynamically within the script.

RSVP. Thanks

Answer 1

The documentation for os.putenv() includes the text:

"... Such changes to the environment affect subprocesses started with os.system(), popen() or fork() and execv()"

So, you can do it like this:

import os

def func_A():
    print os.environ['LANG']
    os._exit(0)  

orig_env = os.environ['LANG']
a_env = orig_env + 'something_else'
os.environ['LANG'] = a_env    

newpid = os.fork()
if newpid == 0:   # this is the child process
    func_A()

... or (maybe better) after the fork() call, like this:

import os

def func_A():
    print os.environ['LANG']
    os._exit(0)  


newpid = os.fork()
if newpid == 0:   # this is the child process
    orig_env = os.environ['LANG']
    a_env = orig_env + 'something_else'
    os.environ['LANG'] = a_env    
    func_A()

(edit) Also the following does appear to work:

module_A.py:

import os
import sys

def func_from_module_A():
    print os.environ['LANG']
    print sys.path
    os._exit(0)  

main.py:

import os
import sys

def startProc_A():
    newpid = os.fork()
    if newpid == 0:   # this is the child process
        orig_env = os.environ['LANG']
        a_env = orig_env + 'something_else'
        os.environ['LANG'] = a_env
        sys.path.append("road_to_nowhere")
        func_A()

def func_A():
    import module_A
    module_A.func_from_module_A()

startProc_A()