gh-65772: Clean-up turtle module (#104218)

* Remove the unused, private, and undocumented name `_ver` and
the commented-out `print` call.

* Don't add math functions to `__all__`.  Beginners should learn
to `import math` to access them.

* Gregor Lindel, who wrote this version of turtle, dropped plans
to implement turtle on another toolkit at least a decade ago.
Drop `_dot` code preparing for this, but add a hint comment.

* `_Screen` is meant to be a singleton class.  To enforce that,
it needs either a `__new__` that returns the singleton or
`else...raise` in `__iter__`.  Merely removing the `if` clauses
as suggested might break something if a user were to call `_Screen`
directly.  Leave the code alone until a problem is evident.

* Turtledemo injects into _Screen both _root and _canvas,
configured as it needs them to be.  Making _canvas an `__init__`
option would require skipping some but not all of the lines under
'if _Screen._canvas is None:`.  Leave working code alone.

Lib/turtle.py

@@ -21,7 +21,6 @@
 #    misrepresented as being the original software.
 # 3. This notice may not be removed or altered from any source distribution.
 
-
 """
 Turtle graphics is a popular way for introducing programming to
 kids. It was part of the original Logo programming language developed
@@ -97,13 +96,8 @@ Roughly it has the following features added:
 
 Behind the scenes there are some features included with possible
 extensions in mind. These will be commented and documented elsewhere.
-
 """
 
-_ver = "turtle 1.1b- - for Python 3.1   -  4. 5. 2009"
-
-# print(_ver)
-
 import tkinter as TK
 import types
 import math
@@ -141,7 +135,7 @@ _tg_turtle_functions = ['back', 'backward', 'begin_fill', 'begin_poly', 'bk',
 _tg_utilities = ['write_docstringdict', 'done']
 
 __all__ = (_tg_classes + _tg_screen_functions + _tg_turtle_functions +
-           _tg_utilities + ['Terminator']) # + _math_functions)
+           _tg_utilities + ['Terminator'])
 
 _alias_list = ['addshape', 'backward', 'bk', 'fd', 'ht', 'lt', 'pd', 'pos',
                'pu', 'rt', 'seth', 'setpos', 'setposition', 'st',
@@ -598,9 +592,6 @@ class TurtleScreenBase(object):
         x0, y0, x1, y1 = self.cv.bbox(item)
         return item, x1-1
 
-##    def _dot(self, pos, size, color):
-##        """may be implemented for some other graphics toolkit"""
-
     def _onclick(self, item, fun, num=1, add=None):
         """Bind fun to mouse-click event on turtle.
         fun must be a function with two arguments, the coordinates
@@ -3455,27 +3446,22 @@ class RawTurtle(TPen, TNavigator):
             if size is None:
                 size = self._pensize + max(self._pensize, 4)
             color = self._colorstr(color)
-        if hasattr(self.screen, "_dot"):
-            item = self.screen._dot(self._position, size, color)
-            self.items.append(item)
-            if self.undobuffer:
-                self.undobuffer.push(("dot", item))
-        else:
-            pen = self.pen()
-            if self.undobuffer:
-                self.undobuffer.push(["seq"])
-                self.undobuffer.cumulate = True
-            try:
-                if self.resizemode() == 'auto':
-                    self.ht()
-                self.pendown()
-                self.pensize(size)
-                self.pencolor(color)
-                self.forward(0)
-            finally:
-                self.pen(pen)
-            if self.undobuffer:
-                self.undobuffer.cumulate = False
+        # If screen were to gain a dot function, see GH #104218.
+        pen = self.pen()
+        if self.undobuffer:
+            self.undobuffer.push(["seq"])
+            self.undobuffer.cumulate = True
+        try:
+            if self.resizemode() == 'auto':
+                self.ht()
+            self.pendown()
+            self.pensize(size)
+            self.pencolor(color)
+            self.forward(0)
+        finally:
+            self.pen(pen)
+        if self.undobuffer:
+            self.undobuffer.cumulate = False
 
     def _write(self, txt, align, font):
         """Performs the writing for write()
@@ -3751,11 +3737,6 @@ class _Screen(TurtleScreen):
     _title = _CFG["title"]
 
     def __init__(self):
-        # 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)

Misc/NEWS.d/next/Library/2023-05-05-18-52-22.gh-issue-65772.w5P5Wv.rst

@@ -0,0 +1 @@
+Remove unneeded comments and code in turtle.py.