environment/lib/python2.7/site-packages/psutil/__init__.py
def process_iter():
    """Return a generator yielding a Process class instance for all
    running processes on the local machine.

    Every new Process instance is only created once and then cached
    into an internal table which is updated every time this is used.

    The sorting order in which processes are yielded is based on
    their PIDs.
    """
    def add(pid):
        proc = Process(pid)
        _pmap[proc.pid] = proc
        return proc

    def remove(pid):
        _pmap.pop(pid, None)

    a = set(get_pid_list())
    b = set(_pmap.keys())
    new_pids = a - b
    gone_pids = b - a

    for pid in gone_pids:
        remove(pid)
    for pid, proc in sorted(list(_pmap.items()) + \
                            list(dict.fromkeys(new_pids).items())):
        try:
            if proc is None:  # new process
                yield add(pid)
            else:
                # use is_running() to check whether PID has been reused by
                # another process in which case yield a new Process instance
                if proc.is_running():
                    yield proc
                else:
                    yield add(pid)
        except NoSuchProcess:
            remove(pid)
        except AccessDenied:
            # Process creation time can't be determined hence there's
            # no way to tell whether the pid of the cached process
            # has been reused. Just return the cached version.
            yield proc
def process_iter():
    """Return a generator yielding a Process class instance for all
    running processes on the local machine.

    Every new Process instance is only created once and then cached
    into an internal table which is updated every time this is used.

    The sorting order in which processes are yielded is based on
    their PIDs.
    """
    def add(pid):
        proc = Process(pid)
        _pmap[proc.pid] = proc
        return proc

    def remove(pid):
        _pmap.pop(pid, None)

    a = set(get_pid_list())
    b = set(_pmap.keys())
    new_pids = a - b
    gone_pids = b - a

    for pid in gone_pids:
        remove(pid)
    for pid, proc in sorted(list(_pmap.items()) + \
                            list(dict.fromkeys(new_pids).items())):
        try:
            if proc is None:  # new process
                yield add(pid)
            else:
                # use is_running() to check whether PID has been reused by
                # another process in which case yield a new Process instance
                if proc.is_running():
                    yield proc
                else:
                    yield add(pid)
        except NoSuchProcess:
            remove(pid)
        except AccessDenied:
            # Process creation time can't be determined hence there's
            # no way to tell whether the pid of the cached process
            # has been reused. Just return the cached version.
            yield proc
Return a generator yielding a Process class instance for all
    running processes on the local machine.

    Every new Process instance is only created once and then cached
    into an internal table which is updated every time this is used.

    The sorting order in which processes are yielded is based on
    their PIDs.