fix 1062: avoid TypeError on disk|net_io_counters() if no disks or NI…

…Cs are installed on the system

HISTORY.rst

@@ -43,6 +43,8 @@
 - 1047_: [Windows] Process username(): memory leak in case exception is thrown.
 - 1048_: [Windows] users()'s host field report an invalid IP address.
 - 1058_: fixed Python warnings.
+- 1062_: disk_io_counters() and net_io_counters() raise TypeError if no disks
+  or NICs are installed on the system.
 
 **Porting notes**
 

psutil/__init__.py

@@ -2083,6 +2083,8 @@ def disk_io_counters(perdisk=False, nowrap=True):
     executed first otherwise this function won't find any disk.
     """
     rawdict = _psplatform.disk_io_counters()
+    if not rawdict:
+        return {} if perdisk else None
     if nowrap:
         rawdict = _wrap_numbers(rawdict, 'psutil.disk_io_counters')
     nt = getattr(_psplatform, "sdiskio", _common.sdiskio)
@@ -2131,6 +2133,8 @@ def net_io_counters(pernic=False, nowrap=True):
     cache.
     """
     rawdict = _psplatform.net_io_counters()
+    if not rawdict:
+        return {} if pernic else None
     if nowrap:
         rawdict = _wrap_numbers(rawdict, 'psutil.net_io_counters')
     if pernic:

psutil/tests/test_system.py

@@ -553,6 +553,15 @@ def check_ntuple(nt):
             self.assertIsInstance(key, str)
             check_ntuple(ret[key])
 
+    def test_net_io_counters_no_nics(self):
+        # Emulate a case where no NICs are installed, see:
+        # https://github.com/giampaolo/psutil/issues/1062
+        with mock.patch('psutil._psplatform.net_io_counters',
+                        return_value={}) as m:
+            self.assertIsNone(psutil.net_io_counters(pernic=False))
+            self.assertEqual(psutil.net_io_counters(pernic=True), {})
+            assert m.called
+
     def test_net_if_addrs(self):
         nics = psutil.net_if_addrs()
         assert nics, nics
@@ -682,6 +691,15 @@ def check_ntuple(nt):
                     key = key[:-1]
                 self.assertNotIn(key, ret.keys())
 
+    def test_disk_io_counters_no_disks(self):
+        # Emulate a case where no disks are installed, see:
+        # https://github.com/giampaolo/psutil/issues/1062
+        with mock.patch('psutil._psplatform.disk_io_counters',
+                        return_value={}) as m:
+            self.assertIsNone(psutil.disk_io_counters(perdisk=False))
+            self.assertEqual(psutil.disk_io_counters(perdisk=True), {})
+            assert m.called
+
     # can't find users on APPVEYOR or TRAVIS
     @unittest.skipIf(APPVEYOR or TRAVIS and not psutil.users(),
                      "unreliable on APPVEYOR or TRAVIS")