diff --git a/Demo/turtle/turtleDemo.py b/Demo/turtle/turtleDemo.py index b73daf090bd..36bf15c7e53 100644 --- a/Demo/turtle/turtleDemo.py +++ b/Demo/turtle/turtleDemo.py @@ -96,8 +96,8 @@ class DemoWindow(object): left_frame.pack(side=LEFT, fill=BOTH, expand=0) self.graph_frame = g_frame = Frame(root) - turtle.Screen._root = g_frame - turtle.Screen._canvas = turtle.ScrolledCanvas(g_frame, 800, 600, 1000, 800) + turtle._Screen._root = g_frame + turtle._Screen._canvas = turtle.ScrolledCanvas(g_frame, 800, 600, 1000, 800) #xturtle.Screen._canvas.pack(expand=1, fill="both") self.screen = _s_ = turtle.Screen() ##### diff --git a/Doc/library/turtle.rst b/Doc/library/turtle.rst index 79297ebbdd2..64df7421ce4 100644 --- a/Doc/library/turtle.rst +++ b/Doc/library/turtle.rst @@ -40,10 +40,10 @@ The object-oriented interface uses essentially two+two classes: :class:`ScrolledCanvas` as argument. It should be used when :mod:`turtle` is used as part of some application. - Derived from :class:`TurtleScreen` is the subclass :class:`Screen`. Screen - is implemented as sort of singleton, so there can exist only one instance of - Screen at a time. It should be used when :mod:`turtle` is used as a - standalone tool for doing graphics. + The function :func:`Screen` returns a singleton object of a + :class:`TurtleScreen` subclass. This function should be used when + :mod:`turtle` is used as a standalone tool for doing graphics. + As a singleton object, inheriting from its class is not possible. All methods of TurtleScreen/Screen also exist as functions, i.e. as part of the procedure-oriented interface. diff --git a/Lib/turtle.py b/Lib/turtle.py index 1497d2d1239..bcc53ce3dd5 100644 --- a/Lib/turtle.py +++ b/Lib/turtle.py @@ -2421,7 +2421,7 @@ class RawTurtle(TPen, TNavigator): shape=_CFG["shape"], undobuffersize=_CFG["undobuffersize"], visible=_CFG["visible"]): - if isinstance(canvas, Screen): + if isinstance(canvas, _Screen): self.screen = canvas elif isinstance(canvas, TurtleScreen): if canvas not in RawTurtle.screens: @@ -3558,29 +3558,33 @@ class RawTurtle(TPen, TNavigator): RawPen = RawTurtle -### Screen - Klasse ######################## +### Screen - Singleton ######################## -class Screen(TurtleScreen): +def Screen(): + """Return the singleton screen object. + If none exists at the moment, create a new one and return it, + else return the existing one.""" + if Turtle._screen is None: + Turtle._screen = _Screen() + return Turtle._screen + +class _Screen(TurtleScreen): _root = None _canvas = None _title = _CFG["title"] - # Borg-Idiom - - _shared_state = {} - - def __new__(cls, *args, **kwargs): - obj = object.__new__(cls, *args, **kwargs) - obj.__dict__ = cls._shared_state - return obj - def __init__(self): - if Screen._root is None: - Screen._root = self._root = _Root() - self._root.title(Screen._title) + # XXX there is no need for this code to be conditional, + # as there will be only a single _Screen instance, anyway + # XXX actually, the turtle demo is injecting root window, + # so perhaps the conditional creation of a root should be + # preserved (perhaps by passing it as an optional parameter) + if _Screen._root is None: + _Screen._root = self._root = _Root() + self._root.title(_Screen._title) self._root.ondestroy(self._destroy) - if Screen._canvas is None: + if _Screen._canvas is None: width = _CFG["width"] height = _CFG["height"] canvwidth = _CFG["canvwidth"] @@ -3588,10 +3592,9 @@ class Screen(TurtleScreen): leftright = _CFG["leftright"] topbottom = _CFG["topbottom"] self._root.setupcanvas(width, height, canvwidth, canvheight) - Screen._canvas = self._root._getcanvas() + _Screen._canvas = self._root._getcanvas() self.setup(width, height, leftright, topbottom) - TurtleScreen.__init__(self, Screen._canvas) - Turtle._screen = self + TurtleScreen.__init__(self, _Screen._canvas) def setup(self, width=_CFG["width"], height=_CFG["height"], startx=_CFG["leftright"], starty=_CFG["topbottom"]): @@ -3645,17 +3648,17 @@ class Screen(TurtleScreen): Example (for a Screen instance named screen): >>> screen.title("Welcome to the turtle-zoo!") """ - if Screen._root is not None: - Screen._root.title(titlestring) - Screen._title = titlestring + if _Screen._root is not None: + _Screen._root.title(titlestring) + _Screen._title = titlestring def _destroy(self): root = self._root - if root is Screen._root: + if root is _Screen._root: Turtle._pen = None Turtle._screen = None - Screen._root = None - Screen._canvas = None + _Screen._root = None + _Screen._canvas = None TurtleScreen._RUNNING = True root.destroy() @@ -3747,7 +3750,7 @@ def write_docstringdict(filename="turtle_docstringdict"): docsdict = {} for methodname in _tg_screen_functions: - key = "Screen."+methodname + key = "_Screen."+methodname docsdict[key] = eval(key).__doc__ for methodname in _tg_turtle_functions: key = "Turtle."+methodname @@ -3862,7 +3865,7 @@ def _screen_docrevise(docstr): for methodname in _tg_screen_functions: - pl1, pl2 = getmethparlist(eval('Screen.' + methodname)) + pl1, pl2 = getmethparlist(eval('_Screen.' + methodname)) if pl1 == "": print(">>>>>>", pl1, pl2) continue @@ -3870,7 +3873,7 @@ for methodname in _tg_screen_functions: {'key':methodname, 'pl1':pl1, 'pl2':pl2}) ## print("Screen:", defstr) exec(defstr) - eval(methodname).__doc__ = _screen_docrevise(eval('Screen.'+methodname).__doc__) + eval(methodname).__doc__ = _screen_docrevise(eval('_Screen.'+methodname).__doc__) for methodname in _tg_turtle_functions: pl1, pl2 = getmethparlist(eval('Turtle.' + methodname)) diff --git a/Misc/NEWS b/Misc/NEWS index d4d0b42edcc..51206bdda41 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -22,6 +22,9 @@ Core and Builtins Library ------- +- Issue #3965: Allow repeated calls to turtle.Screen, by making it a + true singleton object. + - Issue #3911: ftplib.FTP.makeport() could give invalid port numbers. - Issue #3929: When the database cannot be opened, dbm.open() would incorrectly