Turn constants into Enums

[giampaolo]

From g.rodola on January 23, 2014 22:39:11

Future Python 3.4 will include enums: http://www.python.org/dev/peps/pep-0435/ 
Long story short: all python constants in Python 3.4 now look like this:

>>> import socket
>>> socket.SOCK_STREAM
<SocketType.SOCK_STREAM: 1>
>>> 

That is a great step forward in terms of readability because in older Python 
version socket.SOCK_STREAM was just "1" and as such you couldn't immediately 
tell what that was while debugging:

python 2.7:

>>> import socket
>>> socket.socket()
<socket._socketobject object at 0x7f92d08598a0>

python 3.4:

>>> import socket
>>> socket.socket()
<socket.socket fd=3, family=AddressFamily.AF_INET, type=SocketType.SOCK_STREAM, 
proto=0, laddr=('0.0.0.0', 0)>


Same thing applies to psutil. We have different integer constants such as:

>>> psutil.RLIMIT_AS
9
>>> 

...which we could turn into enums so that they'll look like this:

>>> psutil.RLIMIT_AS
<ProcessLimit.RLIMIT_AS: 1>
>>>

For Python versions < 3.4 we can integrate enum.py module straight into 
psutil/_compat.py.

Note to self: figure out what to do with string constants (psutil.CONN_ and 
psutil.STATUS_).

Original issue: http://code.google.com/p/psutil/issues/detail?id=469

[giampaolo]

The following patch turns IOPRIO_CLASS_* and _PRIORITY_CLASS constants returned by psutil.Process.ionice() into enums. Still not sure whether it's the case to implement this because:

• it adds a new ConstIOPriority public class in the psutil namespace
• we should do the same for psutil.AF_LINK, meaning we need another public class / container

    diff --git a/psutil/__init__.py b/psutil/__init__.py
    index a08e645..292e5bb 100644
    --- a/psutil/__init__.py
    +++ b/psutil/__init__.py
    @@ -25,6 +25,10 @@ try:
         import pwd
     except ImportError:
         pwd = None
    +try:
    +    import enum
    +except ImportError:
    +    enum = None

     from ._common import memoize
     from ._compat import callable, long
    @@ -34,6 +38,7 @@ from ._common import (deprecated_method as _deprecated_method,
                           sdiskio as _nt_sys_diskio,
                           snetio as _nt_sys_netio,
                           snic as _nt_snic,
    +                      pionice as _nt_pionice,
                           )

     from ._common import (STATUS_RUNNING,  # NOQA
    @@ -71,6 +76,14 @@ if sys.platform.startswith("linux"):
                                IOPRIO_CLASS_RT,
                                IOPRIO_CLASS_BE,
                                IOPRIO_CLASS_IDLE)
    +
    +    if enum is not None:
    +        ConstIOPriority = enum.IntEnum(
    +            'ConstIOPriority',
    +            dict((name, value) for name, value in globals().items()
    +                 if name.startswith('IOPRIO_') and name.isupper()))
    +        globals().update(ConstIOPriority.__members__)
    +
         # Linux >= 2.6.36
         if _psplatform.HAS_PRLIMIT:
             from ._psutil_linux import (RLIM_INFINITY,  # NOQA
    @@ -111,6 +124,12 @@ if sys.platform.startswith("linux"):
                 pass
             del _psutil_linux

    +        # _RLimit = enum.IntEnum(
    +        #     '_RLimit',
    +        #     dict((name, value) for name, value in globals().items()
    +        #          if name.startswith('RLIM') and name.isupper()))
    +        # globals().update(_RLimit.__members__)
    +
     elif sys.platform.startswith("win32"):
         from . import _pswindows as _psplatform
         from ._psutil_windows import (ABOVE_NORMAL_PRIORITY_CLASS,  # NOQA
    @@ -119,6 +138,14 @@ elif sys.platform.startswith("win32"):
                                       IDLE_PRIORITY_CLASS,
                                       NORMAL_PRIORITY_CLASS,
                                       REALTIME_PRIORITY_CLASS)
    +
    +    if enum is not None:
    +        ConstIOPriority = enum.IntEnum(
    +            'ConstIOPriority',
    +            dict((name, value) for name, value in globals().items()
    +                 if name.endsswith('_PRIORITY_CLASS') and name.isupper()))
    +        globals().update(ConstIOPriority.__members__)
    +
         from ._pswindows import CONN_DELETE_TCB  # NOQA

     elif sys.platform.startswith("darwin"):
    @@ -665,7 +692,10 @@ class Process(object):
                 if ioclass is None:
                     if value is not None:
                         raise ValueError("'ioclass' must be specified")
    -                return self._proc.ionice_get()
    +                ioclass, value = self._proc.ionice_get()
    +                if enum is not None:
    +                    ioclass = ConstIOPriority(ioclass)
    +                return _nt_pionice(ioclass, value)
                 else:
                     return self._proc.ionice_set(ioclass, value)

    diff --git a/psutil/_pslinux.py b/psutil/_pslinux.py
    index c21d089..ec6495c 100644
    --- a/psutil/_pslinux.py
    +++ b/psutil/_pslinux.py
    @@ -973,8 +973,7 @@ class Process(object):

             @wrap_exceptions
             def ionice_get(self):
    -            ioclass, value = cext.proc_ioprio_get(self.pid)
    -            return _common.pionice(ioclass, value)
    +            return cext.proc_ioprio_get(self.pid)

             @wrap_exceptions
             def ionice_set(self, ioclass, value):
    diff --git a/test/test_psutil.py b/test/test_psutil.py
    index efbcead..8a73ac2 100644
    --- a/test/test_psutil.py
    +++ b/test/test_psutil.py
    @@ -46,6 +46,10 @@ try:
         import ipaddress  # python >= 3.3
     except ImportError:
         ipaddress = None
    +try:
    +    import enum  # python >= 3.4
    +except ImportError:
    +    enum = None

     try:
         import enum  # python >= 3.4
    @@ -1380,6 +1384,8 @@ class TestProcess(unittest.TestCase):
                 try:
                     p.ionice(2)
                     ioclass, value = p.ionice()
    +                if enum is not None:
    +                    self.assertIsInstance(ioclass, enum.IntEnum)
                     self.assertEqual(ioclass, 2)
                     self.assertEqual(value, 4)
                     #
    @@ -1432,6 +1438,8 @@ class TestProcess(unittest.TestCase):
                     self.assertEqual(len(ret), 2)
                     self.assertGreaterEqual(ret[0], -1)
                     self.assertGreaterEqual(ret[1], -1)
    +            if enum is not None:
    +                self.assertIsInstance(getattr(psutil, name), enum.IntEnum)

         @unittest.skipUnless(LINUX and RLIMIT_SUPPORT,
                              "only available on Linux >= 2.6.36")

[giampaolo]

For now I opted for converting IOPRIO_CLASS_* and *_PRIORITY_CLASS constants into enums on Python 3.4 only. enum might be installed as a third party dep on Python < 3.4 (see https://pypi.python.org/pypi/enum34/) but I decided not to assume that and explicitly ignore Python < 3.4 'cause the JSON module can't serialize those objects.