issue12085: Use more Pythonic way to check _child_created.

_active shouldn't be cached, it set to None on shutdown.

Lib/subprocess.py

@@ -645,6 +645,8 @@ def list2cmdline(seq):
 
 
 class Popen(object):
+    _child_created = False  # Set here since __del__ checks it
+
     def __init__(self, args, bufsize=0, executable=None,
                  stdin=None, stdout=None, stderr=None,
                  preexec_fn=None, close_fds=False, shell=False,
@@ -653,7 +655,6 @@ class Popen(object):
         """Create new Popen instance."""
         _cleanup()
 
-        self._child_created = False
         if not isinstance(bufsize, (int, long)):
             raise TypeError("bufsize must be an integer")
 
@@ -750,11 +751,11 @@ class Popen(object):
         return data
 
 
-    def __del__(self, _maxint=sys.maxint, _active=_active):
+    def __del__(self, _maxint=sys.maxint):
         # If __init__ hasn't had a chance to execute (e.g. if it
         # was passed an undeclared keyword argument), we don't
         # have a _child_created attribute at all.
-        if not getattr(self, '_child_created', False):
+        if not self._child_created:
             # We didn't get to successfully create a child process.
             return
         # In case the child hasn't been waited on, check if it's done.
@@ -1330,7 +1331,7 @@ class Popen(object):
                 _WTERMSIG=os.WTERMSIG, _WIFEXITED=os.WIFEXITED,
                 _WEXITSTATUS=os.WEXITSTATUS):
             # This method is called (indirectly) by __del__, so it cannot
-            # refer to anything outside of its local scope."""
+            # refer to anything outside of its local scope.
             if _WIFSIGNALED(sts):
                 self.returncode = -_WTERMSIG(sts)
             elif _WIFEXITED(sts):