MSS: use __slots__ for better performances

Using sys.getsizeof(sct) shows interesting improvements:
- GNU/Linux: 104 -> 88
- macOS: 80 -> 64
- Windows: 112 -> 64

CHANGELOG

@@ -5,6 +5,7 @@ History:
 5.0.0   2019/xx/xx
       - removed support for Python 2.7
       - MSS: improve type annotations and add CI check
+      - MSS: use __slots__ for better performances
       - Windows: use our own instances of GDI32 and User32 DLLs
       - doc: add an example using the multiprocessing module (closes #82)
 

CHANGES.rst

@@ -1,8 +1,13 @@
 5.0.0 (2019-xx-xx)
 ==================
 
+darwin.py
+---------
+- Added `MSS.__slots__`
+
 linux.py
 --------
+- Added `MSS.__slots__`
 - Deleted ``LAST_ERROR`` constant. Use ``ERROR`` namespace instead, specially the ``ERROR.details`` attribute.
 
 models.py
@@ -16,9 +21,14 @@ models.py
 
 screenshot.py
 -------------
+- Added `ScreenShot.__slots__`
 - Removed ``Pos``. Use ``models.Pos`` instead.
 - Removed ``Size``. Use ``models.Size`` instead.
 
+windows.py
+----------
+- Added `MSS.__slots__`
+
 
 4.0.1 (2019-01-26)
 ==================

mss/base.py

@@ -19,8 +19,12 @@
 class MSSMixin:
     """ This class will be overloaded by a system specific one. """
 
-    cls_image = ScreenShot  # type: Type[ScreenShot]
-    compression_level = 6
+    __slots__ = {"_monitors", "cls_image", "compression_level"}
+
+    def __init__(self):
+        self.cls_image = ScreenShot  # type: Type[ScreenShot]
+        self.compression_level = 6
+        self._monitors = []  # type: Monitors
 
     def __enter__(self):
         # type: () -> MSSMixin

mss/darwin.py

@@ -63,10 +63,13 @@ class MSS(MSSMixin):
     It uses intensively the CoreGraphics library.
     """
 
+    __slots__ = {"core", "max_displays"}
+
     def __init__(self, **_):
         """ macOS initialisations. """
 
-        self._monitors = []  # type: Monitors
+        super().__init__()
+
         self.max_displays = 32
 
         coregraphics = ctypes.util.find_library("CoreGraphics")

mss/linux.py

@@ -181,11 +181,13 @@ class MSS(MSSMixin):
     It uses intensively the Xlib and its Xrandr extension.
     """
 
+    __slots__ = {"display", "drawable", "root", "xlib", "xrandr"}
+
     def __init__(self, display=None):
         # type: (Optional[Union[bytes, str]]) -> None
         """ GNU/Linux initialisations. """
 
-        self._monitors = []  # type: Monitors
+        super().__init__()
 
         if not display:
             try:

mss/screenshot.py

@@ -24,6 +24,8 @@ class ScreenShot:
         with PIL.Image, it has been decided to use *ScreenShot*.
     """
 
+    __slots__ = {"__pixels", "__rgb", "pos", "raw", "size"}
+
     def __init__(self, data, monitor, size=None):
         # type: (bytearray, Monitor, Optional[Size]) -> None
 

mss/windows.py

@@ -67,11 +67,24 @@ class BITMAPINFO(ctypes.Structure):
 class MSS(MSSMixin):
     """ Multiple ScreenShots implementation for Microsoft Windows. """
 
+    __slots__ = {
+        "_bbox",
+        "_bmi",
+        "_bmp",
+        "_data",
+        "_memdc",
+        "_srcdc",
+        "gdi32",
+        "monitorenumproc",
+        "user32",
+    }
+
     def __init__(self, **_):
         # type: (Any) -> None
         """ Windows initialisations. """
 
-        self._monitors = []  # type: Monitors
+        super().__init__()
+
         self._bbox = {"height": 0, "width": 0}
         self._bmp = None
         self._data = ctypes.create_string_buffer(0)  # type: ctypes.Array[ctypes.c_char]

tests/test_windows.py

@@ -3,7 +3,6 @@
 Source: https://github.com/BoboTiG/python-mss
 """
 
-import ctypes.util
 import platform
 
 import mss
@@ -18,6 +17,6 @@
 def test_implementation(monkeypatch):
     # Test bad data retrieval
     with mss.mss() as sct:
-        monkeypatch.setattr(ctypes.windll.gdi32, "GetDIBits", lambda *args: 0)
+        monkeypatch.setattr(sct.gdi32, "GetDIBits", lambda *args: 0)
         with pytest.raises(ScreenShotError):
             sct.shot()