# Buggy code
def ppid(self):
    """The process parent PID.
    On Windows the return value is cached after first call.
    """
    # On POSIX we don't want to cache the ppid as it may unexpectedly
    # change to 1 (init) in case this process turns into a zombie:
    # https://github.com/giampaolo/psutil/issues/321
    # http://stackoverflow.com/questions/356722/

    # XXX should we check creation time here rather than in
    # Process.parent()?
    if _POSIX:
        return self._proc.ppid()
    else:
        if self._ppid is None:
            self._ppid = self._proc.ppid()
        return self._ppid


# Traceback (psutil._error.NoSuchProcess)
How to reproduce:

1. start Photoshop CS6 on a Mountain Lion OSX
2. import psutil; [x.as_dict() for x in psutil.process_iter()] # (in .py file, ipython)



What is the expected output?
A long list of processes and related information



What do you see instead?


$ python test.py
Traceback (most recent call last):
File "test.py", line 3, in <module>
[x.as_dict() for x in psutil.process_iter() if x.is_running()]
File
"/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/__init__.py",
line 225, in as_dict
ret = attr()
File
"/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/__init__.py",
line 414, in get_nice
return self._platform_impl.get_process_nice()
File
"/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/_psosx.py",
line 151, in wrapper
raise NoSuchProcess(self.pid, self._process_name)
psutil._error.NoSuchProcess: process no longer exists (pid=46244)

or within iPython notebook:
[x.as_dict() for x in psutil.process_iter() if x.is_running()]
---------------------------------------------------------------------------
NoSuchProcess                             Traceback (most recent call last)
<ipython-input-108-a71c6dffe397> in <module>()
----> 1 [x.as_dict() for x in psutil.process_iter() if x.is_running()]

/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/__init__.pyc
in as_dict(self, attrs, ad_value)
223                         ret = attr(interval=0)
224                     else:
--> 225                         ret = attr()
226                 else:
227                     ret = attr

/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/__init__.pyc
in get_nice(self)
412     def get_nice(self):
413         """Get process niceness (priority)."""
--> 414         return self._platform_impl.get_process_nice()
415
416     @_assert_pid_not_reused

/Users/rico/.virtualenvs/temp/lib/python2.7/site-packages/psutil/_psosx.pyc in
wrapper(self, *args, **kwargs)
149             err = sys.exc_info()[1]
150             if err.errno == errno.ESRCH:
--> 151                 raise NoSuchProcess(self.pid, self._process_name)
152             if err.errno in (errno.EPERM, errno.EACCES):
153                 raise AccessDenied(self.pid, self._process_name)

NoSuchProcess: process no longer exists (pid=46243, name='adobe_licutil')

When I close Photoshop, the error will not show up. When starting it again the
error reappears.
An additional is_running() check within the list comprehension does not change
a thing and running the code several times will not change the reported pid.

# Fixed code
def ppid(self):
    """The process parent PID.
    On Windows the return value is cached after first call.
    """
    # On POSIX we don't want to cache the ppid as it may unexpectedly
    # change to 1 (init) in case this process turns into a zombie:
    # https://github.com/giampaolo/psutil/issues/321
    # http://stackoverflow.com/questions/356722/

    # XXX should we check creation time here rather than in
    # Process.parent()?
    if _POSIX:
        ppid = self._proc.ppid()
    else:
        if self._ppid is None:
            ppid = self._proc.ppid()
        self._ppid = ppid
    self._proc._ppid = ppid
    return ppid