run_me.py: 
import subprocess, sys
e = {'PATH_TO_MY_APPS' : "path/to/my/apps"}
p = subprocess.Popen(sys.executable + " test1.py 123", env=e, shell=True, stdout=subprocess.PIPE)
print(p.stdout.readlines())
p.wait()


test1.py:
1: import sys, os
2: #import tempfile
3: print("hello : " + sys.platform + " PATH: " + os.environ['PATH_TO_MY_APPS'])

System:
Python 2.7.2 x64, Windows x64 7 Pro + SP1

Problem:
if I run python run_me.py then I see on my stdout:
['hello : win32 PATH: path/to/my/apps\r\n']

but if I uncomment line number 2 in test1.py  and run python run_me.py then I see on my stdout :

C:\tmp\python_test>python run_me.py
Traceback (most recent call last):
  File "test1.py", line 2, in <module>
    import tempfile
  File "C:\Python27\lib\tempfile.py", line 34, in <module>
    from random import Random as _Random
  File "C:\Python27\lib\random.py", line 883, in <module>
    _inst = Random()
  File "C:\Python27\lib\random.py", line 97, in __init__
    self.seed(x)
  File "C:\Python27\lib\random.py", line 111, in seed
    a = long(_hexlify(_urandom(16)), 16)
WindowsError: [Error -2146893818] Invalid Signature
[]

WIDW ?

The environment passed to a Windows process must contain
certain things. (I don't at this moment remember exactly
what). You can't just pass the one thing you're adding.
Change your "e = ..." line to something like:

e = os.environ
e['PATH_TO_MY_CODE'] = '/x/y/z'

and then try the code.

Obviously the subprocess module doesn't have enough
checks in place for this -- it actually segfaults on my
WinXP machine. But can you confirm that this is indeed
your issue?

it fix my problem:

e = os.environ.copy()
e['PATH_TO_MY_APPS'] = "path/to/my/apps"

p = subprocess.Popen(sys.executable + " test1.py 123", env=e, shell=True, stdout=subprocess.PIPE)

answer: need have copy of environments

Re-opening because there's a real problem here which can crash Python hard. Simplest reproduction:

import sys
import subprocess

subprocess.Popen (sys.executable, env={})

Affects 2.x and 3.x tip (haven't tried others yet but I don't imagine it's different)

> Re-opening because there's a real problem here which can crash Python
> hard.

Works under Linux. Is it Windows-specific?

Yes. I've added the "Windows" component on the tracker.
(At least I think I have). It's to do with CreateProcess
needing at least certain items in the environment passed.
I'm trying to track down some docs on MSDN which specify
which must be there.

OK, the long and short is that spwaning a process without passing
in SystemRoot is asking for trouble. There's a blog post here
which gives an example:

http://jpassing.com/2009/12/28/the-hidden-danger-of-forgetting-to-specify-systemroot-in-a-custom-environment-block/

And, certainly this works:

import os
import subprocess
subprocess.Popen(
     "notepad.exe",
     env={"SystemRoot" : os.environ['SystemRoot']}
)

I'm not quite sure what approach we should take in the subprocess
module. Is it a docs warning? Should we refuse to proceed if there's
no SystemRoot? Is it the caller's responsibility?
I'll ask on python-dev to gather opinions.

After a discussion on python-dev:

   http://mail.python.org/pipermail/python-dev/2011-December/114733.html

I propose to close this call tomorrow as wontfix