Harmonize docstrings. Move redemo from Tools/scripts to Tools/demo. Add a README file to Tools/demo.

14 files changed, 367 insertions, 149 deletions

diff --git a/Tools/demo/README b/Tools/demo/README
new file mode 100644
index 0000000..e914358
--- /dev/null
+++ b/Tools/demo/README
@@ -0,0 +1,16 @@
+This directory contains a collection of demonstration scripts for
+various aspects of Python programming.
+
+beer.py        Well-known programming example: Bottles of beer.
+eiffel.py      Python advanced magic: A metaclass for Eiffel post/preconditions.
+hanoi.py       Well-known programming example: Towers of Hanoi.
+life.py        Curses programming: Simple game-of-life.
+markov.py      Algorithms: Markov chain simulation.
+mcast.py       Network programming: Send and receive UDP multicast packets.
+queens.py      Well-known programming example: N-Queens problem.
+redemo.py      Regular Expressions: GUI script to test regexes.
+rpython.py     Network programming: Small client for remote code execution.
+rpythond.py    Network programming: Small server for remote code execution.
+sortvisu.py    GUI programming: Visualization of different sort algorithms.
+ss1.py         GUI/Application programming: A simple spreadsheet application.
+vector.py      Python basics: A vector class with demonstrating special methods.
\ No newline at end of file
diff --git a/Tools/demo/beer.py b/Tools/demo/beer.py
index 56eec7b..af58380 100755
--- a/Tools/demo/beer.py
+++ b/Tools/demo/beer.py
@@ -1,6 +1,11 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
 
-# By GvR, demystified after a version by Fredrik Lundh.
+"""
+A Python version of the classic "bottles of beer on the wall" programming
+example.
+
+By Guido van Rossum, demystified after a version by Fredrik Lundh.
+"""
 
 import sys
 
diff --git a/Tools/demo/Eiffel.py b/Tools/demo/eiffel.py
index 15fa58a..3a28224 100644..100755
--- a/Tools/demo/Eiffel.py
+++ b/Tools/demo/eiffel.py
@@ -1,13 +1,20 @@
-"""Support Eiffel-style preconditions and postconditions."""
+#!/usr/bin/env python3
 
+"""
+Support Eiffel-style preconditions and postconditions for functions.
+
+An example for Python metaclasses.
+"""
+
+import unittest
 from types import FunctionType as function
 
 class EiffelBaseMetaClass(type):
 
     def __new__(meta, name, bases, dict):
         meta.convert_methods(dict)
-        return super(EiffelBaseMetaClass, meta).__new__(meta, name, bases,
-                                                        dict)
+        return super(EiffelBaseMetaClass, meta).__new__(
+            meta, name, bases, dict)
 
     @classmethod
     def convert_methods(cls, dict):
@@ -31,6 +38,7 @@ class EiffelBaseMetaClass(type):
             if pre or post:
                 dict[k] = cls.make_eiffel_method(dict[m], pre, post)
 
+
 class EiffelMetaClass1(EiffelBaseMetaClass):
     # an implementation of the "eiffel" meta class that uses nested functions
 
@@ -39,16 +47,17 @@ class EiffelMetaClass1(EiffelBaseMetaClass):
         def method(self, *args, **kwargs):
             if pre:
                 pre(self, *args, **kwargs)
-            x = func(self, *args, **kwargs)
+            rv = func(self, *args, **kwargs)
             if post:
-                post(self, x, *args, **kwargs)
-            return x
+                post(self, rv, *args, **kwargs)
+            return rv
 
         if func.__doc__:
             method.__doc__ = func.__doc__
 
         return method
 
+
 class EiffelMethodWrapper:
 
     def __init__(self, inst, descr):
@@ -58,7 +67,8 @@ class EiffelMethodWrapper:
     def __call__(self, *args, **kwargs):
         return self._descr.callmethod(self._inst, args, kwargs)
 
-class EiffelDescriptor(object):
+
+class EiffelDescriptor:
 
     def __init__(self, func, pre, post):
         self._func = func
@@ -79,63 +89,58 @@ class EiffelDescriptor(object):
             self._post(inst, x, *args, **kwargs)
         return x
 
+
 class EiffelMetaClass2(EiffelBaseMetaClass):
     # an implementation of the "eiffel" meta class that uses descriptors
 
     make_eiffel_method = EiffelDescriptor
 
-def _test(metaclass):
-    class Eiffel(metaclass=metaclass):
-        pass
-
-    class Test(Eiffel):
-
-        def m(self, arg):
-            """Make it a little larger"""
-            return arg + 1
-
-        def m2(self, arg):
-            """Make it a little larger"""
-            return arg + 1
-
-        def m2_pre(self, arg):
-            assert arg > 0
-
-        def m2_post(self, result, arg):
-            assert result > arg
-
-    class Sub(Test):
-        def m2(self, arg):
-            return arg**2
-        def m2_post(self, Result, arg):
-            super(Sub, self).m2_post(Result, arg)
-            assert Result < 100
-
-    t = Test()
-    t.m(1)
-    t.m2(1)
-    try:
-        t.m2(0)
-    except AssertionError:
-        pass
-    else:
-        assert False
-
-    s = Sub()
-    try:
-        s.m2(1)
-    except AssertionError:
-        pass # result == arg
-    else:
-        assert False
-    try:
-        s.m2(10)
-    except AssertionError:
-        pass # result ==  100
-    else:
-        assert False
-    s.m2(5)
+
+class Tests(unittest.TestCase):
+
+    def testEiffelMetaClass1(self):
+        self._test(EiffelMetaClass1)
+
+    def testEiffelMetaClass2(self):
+        self._test(EiffelMetaClass2)
+
+    def _test(self, metaclass):
+        class Eiffel(metaclass=metaclass):
+            pass
+
+        class Test(Eiffel):
+            def m(self, arg):
+                """Make it a little larger"""
+                return arg + 1
+
+            def m2(self, arg):
+                """Make it a little larger"""
+                return arg + 1
+
+            def m2_pre(self, arg):
+                assert arg > 0
+
+            def m2_post(self, result, arg):
+                assert result > arg
+
+        class Sub(Test):
+            def m2(self, arg):
+                return arg**2
+
+            def m2_post(self, Result, arg):
+                super(Sub, self).m2_post(Result, arg)
+                assert Result < 100
+
+        t = Test()
+        self.assertEqual(t.m(1), 2)
+        self.assertEqual(t.m2(1), 2)
+        self.assertRaises(AssertionError, t.m2, 0)
+
+        s = Sub()
+        self.assertRaises(AssertionError, s.m2, 1)
+        self.assertRaises(AssertionError, s.m2, 10)
+        self.assertEqual(s.m2(5), 25)
+
 
 if __name__ == "__main__":
-    _test(EiffelMetaClass1)
-    _test(EiffelMetaClass2)
+    unittest.main()
diff --git a/Tools/demo/hanoi.py b/Tools/demo/hanoi.py
index 34a0bba..dad0234 100644..100755
--- a/Tools/demo/hanoi.py
+++ b/Tools/demo/hanoi.py
@@ -1,17 +1,18 @@
-# Animated Towers of Hanoi using Tk with optional bitmap file in
-# background.
-#
-# Usage: tkhanoi [n [bitmapfile]]
-#
-# n is the number of pieces to animate; default is 4, maximum 15.
-#
-# The bitmap file can be any X11 bitmap file (look in
-# /usr/include/X11/bitmaps for samples); it is displayed as the
-# background of the animation.  Default is no bitmap.
+#!/usr/bin/env python3
 
-# This uses Steen Lumholt's Tk interface
-from tkinter import *
+"""
+Animated Towers of Hanoi using Tk with optional bitmap file in background.
 
+Usage: hanoi.py [n [bitmapfile]]
+
+n is the number of pieces to animate; default is 4, maximum 15.
+
+The bitmap file can be any X11 bitmap file (look in /usr/include/X11/bitmaps for
+samples); it is displayed as the background of the animation.  Default is no
+bitmap.
+"""
+
+from tkinter import Tk, Canvas
 
 # Basic Towers-of-Hanoi algorithm: move n pieces from a to b, using c
 # as temporary.  For each move, call report()
@@ -123,7 +124,6 @@ class Tkhanoi:
         self.pegstate[b].append(i)
 
 
-# Main program
 def main():
     import sys
 
diff --git a/Tools/demo/life.py b/Tools/demo/life.py
index 3cbc053..dfb9ab8 100755
--- a/Tools/demo/life.py
+++ b/Tools/demo/life.py
@@ -1,23 +1,23 @@
 #!/usr/bin/env python3
-# life.py -- A curses-based version of Conway's Game of Life.
-# Contributed by AMK
-# Mouse support and color by Dafydd Crosby
-#
-# An empty board will be displayed, and the following commands are available:
-#  E : Erase the board
-#  R : Fill the board randomly
-#  S : Step for a single generation
-#  C : Update continuously until a key is struck
-#  Q : Quit
-#  Cursor keys :  Move the cursor around the board
-#  Space or Enter : Toggle the contents of the cursor's position
-#
-# TODO :
-#   Make board updates faster
-#
-
-import random, string, traceback
+
+"""
+A curses-based version of Conway's Game of Life.
+
+An empty board will be displayed, and the following commands are available:
+ E : Erase the board
+ R : Fill the board randomly
+ S : Step for a single generation
+ C : Update continuously until a key is struck
+ Q : Quit
+ Cursor keys :  Move the cursor around the board
+ Space or Enter : Toggle the contents of the cursor's position
+
+Contributed by Andrew Kuchling, Mouse support and color by Dafydd Crosby.
+"""
+
 import curses
+import random
+
 
 class LifeBoard:
     """Encapsulates a Life board
@@ -31,7 +31,7 @@ class LifeBoard:
                              next generation.  Then display the state
                              of the board and refresh the screen.
     erase() -- clear the entire board
-    makeRandom() -- fill the board randomly
+    make_random() -- fill the board randomly
     set(y,x) -- set the given cell to Live; doesn't refresh the screen
     toggle(y,x) -- change the given cell from live to dead, or vice
                    versa, and refresh the screen display
@@ -53,7 +53,7 @@ class LifeBoard:
         # Draw a border around the board
         border_line = '+'+(self.X*'-')+'+'
         self.scr.addstr(0, 0, border_line)
-        self.scr.addstr(self.Y+1,0, border_line)
+        self.scr.addstr(self.Y+1, 0, border_line)
         for y in range(0, self.Y):
             self.scr.addstr(1+y, 0, '|')
             self.scr.addstr(1+y, self.X+1, '|')
@@ -62,21 +62,21 @@ class LifeBoard:
     def set(self, y, x):
         """Set a cell to the live state"""
         if x<0 or self.X<=x or y<0 or self.Y<=y:
-            raise ValueError("Coordinates out of range %i,%i"% (y,x))
+            raise ValueError("Coordinates out of range %i,%i"% (y, x))
         self.state[x,y] = 1
 
     def toggle(self, y, x):
         """Toggle a cell's state between live and dead"""
-        if x<0 or self.X<=x or y<0 or self.Y<=y:
-            raise ValueError("Coordinates out of range %i,%i"% (y,x))
-        if (x,y) in self.state:
-            del self.state[x,y]
+        if x < 0 or self.X <= x or y < 0 or self.Y <= y:
+            raise ValueError("Coordinates out of range %i,%i"% (y, x))
+        if (x, y) in self.state:
+            del self.state[x, y]
             self.scr.addch(y+1, x+1, ' ')
         else:
-            self.state[x,y] = 1
+            self.state[x, y] = 1
             if curses.has_colors():
-                #Let's pick a random color!
-                self.scr.attrset(curses.color_pair(random.randrange(1,7)))
+                # Let's pick a random color!
+                self.scr.attrset(curses.color_pair(random.randrange(1, 7)))
             self.scr.addch(y+1, x+1, self.char)
             self.scr.attrset(0)
         self.scr.refresh()
@@ -115,8 +115,9 @@ class LifeBoard:
                     # Birth
                     d[i,j] = 1
                     if curses.has_colors():
-                        #Let's pick a random color!
-                        self.scr.attrset(curses.color_pair(random.randrange(1,7)))
+                        # Let's pick a random color!
+                        self.scr.attrset(curses.color_pair(
+                            random.randrange(1, 7)))
                     self.scr.addch(j+1, i+1, self.char)
                     self.scr.attrset(0)
                     if not live: self.boring = 0
@@ -128,7 +129,7 @@ class LifeBoard:
         self.state = d
         self.scr.refresh()
 
-    def makeRandom(self):
+    def make_random(self):
         "Fill the board with a random pattern"
         self.state = {}
         for i in range(0, self.X):
@@ -152,9 +153,9 @@ def display_menu(stdscr, menu_y):
     if curses.has_colors():
         stdscr.attrset(curses.color_pair(1))
     stdscr.addstr(menu_y, 4,
-                  'Use the cursor keys to move, and space or Enter to toggle a cell.')
+        'Use the cursor keys to move, and space or Enter to toggle a cell.')
     stdscr.addstr(menu_y+1, 4,
-                  'E)rase the board, R)andom fill, S)tep once or C)ontinuously, Q)uit')
+        'E)rase the board, R)andom fill, S)tep once or C)ontinuously, Q)uit')
     stdscr.attrset(0)
 
 def keyloop(stdscr):
@@ -186,10 +187,10 @@ def keyloop(stdscr):
     xpos, ypos = board.X//2, board.Y//2
 
     # Main loop:
-    while (1):
+    while True:
         stdscr.move(1+ypos, 1+xpos)     # Move the cursor
         c = stdscr.getch()                # Get a keystroke
-        if 0<c<256:
+        if 0 < c < 256:
             c = chr(c)
             if c in ' \n':
                 board.toggle(ypos, xpos)
@@ -201,14 +202,14 @@ def keyloop(stdscr):
                 # Activate nodelay mode; getch() will return -1
                 # if no keystroke is available, instead of waiting.
                 stdscr.nodelay(1)
-                while (1):
+                while True:
                     c = stdscr.getch()
                     if c != -1:
                         break
-                    stdscr.addstr(0,0, '/')
+                    stdscr.addstr(0, 0, '/')
                     stdscr.refresh()
                     board.display()
-                    stdscr.addstr(0,0, '+')
+                    stdscr.addstr(0, 0, '+')
                     stdscr.refresh()
 
                 stdscr.nodelay(0)       # Disable nodelay mode
@@ -219,18 +220,19 @@ def keyloop(stdscr):
             elif c in 'Qq':
                 break
             elif c in 'Rr':
-                board.makeRandom()
+                board.make_random()
                 board.display(update_board=False)
             elif c in 'Ss':
                 board.display()
             else: pass                  # Ignore incorrect keys
-        elif c == curses.KEY_UP and ypos>0:            ypos -= 1
-        elif c == curses.KEY_DOWN and ypos<board.Y-1:  ypos += 1
-        elif c == curses.KEY_LEFT and xpos>0:          xpos -= 1
-        elif c == curses.KEY_RIGHT and xpos<board.X-1: xpos += 1
+        elif c == curses.KEY_UP and ypos > 0:            ypos -= 1
+        elif c == curses.KEY_DOWN and ypos < board.Y-1:  ypos += 1
+        elif c == curses.KEY_LEFT and xpos > 0:          xpos -= 1
+        elif c == curses.KEY_RIGHT and xpos < board.X-1: xpos += 1
         elif c == curses.KEY_MOUSE:
-            (mouse_id, mouse_x, mouse_y, mouse_z, button_state) = curses.getmouse()
-            if (mouse_x>0 and mouse_x<board.X+1) and (mouse_y>0 and mouse_y<board.Y+1):
+            mouse_id, mouse_x, mouse_y, mouse_z, button_state = curses.getmouse()
+            if (mouse_x > 0 and mouse_x < board.X+1 and
+                mouse_y > 0 and mouse_y < board.Y+1):
                 xpos = mouse_x - 1
                 ypos = mouse_y - 1
                 board.toggle(ypos, xpos)
@@ -245,6 +247,5 @@ def keyloop(stdscr):
 def main(stdscr):
     keyloop(stdscr)                    # Enter the main loop
 
-
 if __name__ == '__main__':
     curses.wrapper(main)
diff --git a/Tools/demo/markov.py b/Tools/demo/markov.py
index 7c08bdb..7a0720f 100755
--- a/Tools/demo/markov.py
+++ b/Tools/demo/markov.py
@@ -1,4 +1,8 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
+
+"""
+Markov chain simulation of words or characters.
+"""
 
 class Markov:
     def __init__(self, histsize, choice):
diff --git a/Tools/demo/mcast.py b/Tools/demo/mcast.py
index 6ce7c6d..924c7c3 100755
--- a/Tools/demo/mcast.py
+++ b/Tools/demo/mcast.py
@@ -1,13 +1,15 @@
 #!/usr/bin/env python3
-#
-# Send/receive UDP multicast packets.
-# Requires that your OS kernel supports IP multicast.
-#
-# Usage:
-#   mcast -s (sender, IPv4)
-#   mcast -s -6 (sender, IPv6)
-#   mcast    (receivers, IPv4)
-#   mcast  -6  (receivers, IPv6)
+
+"""
+Send/receive UDP multicast packets.
+Requires that your OS kernel supports IP multicast.
+
+Usage:
+  mcast -s (sender, IPv4)
+  mcast -s -6 (sender, IPv6)
+  mcast    (receivers, IPv4)
+  mcast  -6  (receivers, IPv6)
+"""
 
 MYPORT = 8123
 MYGROUP_4 = '225.0.0.250'
diff --git a/Tools/demo/queens.py b/Tools/demo/queens.py
index ffd4bea..dcc1bae 100755
--- a/Tools/demo/queens.py
+++ b/Tools/demo/queens.py
@@ -1,12 +1,12 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
 
-"""N queens problem.
+"""
+N queens problem.
 
 The (well-known) problem is due to Niklaus Wirth.
 
 This solution is inspired by Dijkstra (Structured Programming).  It is
 a classic recursive backtracking approach.
-
 """
 
 N = 8                                   # Default; command line overrides
diff --git a/Tools/demo/redemo.py b/Tools/demo/redemo.py
new file mode 100644
index 0000000..5286332
--- /dev/null
+++ b/Tools/demo/redemo.py
@@ -0,0 +1,171 @@
+"""Basic regular expression demostration facility (Perl style syntax)."""
+
+from tkinter import *
+import re
+
+class ReDemo:
+
+    def __init__(self, master):
+        self.master = master
+
+        self.promptdisplay = Label(self.master, anchor=W,
+                text="Enter a Perl-style regular expression:")
+        self.promptdisplay.pack(side=TOP, fill=X)
+
+        self.regexdisplay = Entry(self.master)
+        self.regexdisplay.pack(fill=X)
+        self.regexdisplay.focus_set()
+
+        self.addoptions()
+
+        self.statusdisplay = Label(self.master, text="", anchor=W)
+        self.statusdisplay.pack(side=TOP, fill=X)
+
+        self.labeldisplay = Label(self.master, anchor=W,
+                text="Enter a string to search:")
+        self.labeldisplay.pack(fill=X)
+        self.labeldisplay.pack(fill=X)
+
+        self.showframe = Frame(master)
+        self.showframe.pack(fill=X, anchor=W)
+
+        self.showvar = StringVar(master)
+        self.showvar.set("first")
+
+        self.showfirstradio = Radiobutton(self.showframe,
+                                         text="Highlight first match",
+                                          variable=self.showvar,
+                                          value="first",
+                                          command=self.recompile)
+        self.showfirstradio.pack(side=LEFT)
+
+        self.showallradio = Radiobutton(self.showframe,
+                                        text="Highlight all matches",
+                                        variable=self.showvar,
+                                        value="all",
+                                        command=self.recompile)
+        self.showallradio.pack(side=LEFT)
+
+        self.stringdisplay = Text(self.master, width=60, height=4)
+        self.stringdisplay.pack(fill=BOTH, expand=1)
+        self.stringdisplay.tag_configure("hit", background="yellow")
+
+        self.grouplabel = Label(self.master, text="Groups:", anchor=W)
+        self.grouplabel.pack(fill=X)
+
+        self.grouplist = Listbox(self.master)
+        self.grouplist.pack(expand=1, fill=BOTH)
+
+        self.regexdisplay.bind('<Key>', self.recompile)
+        self.stringdisplay.bind('<Key>', self.reevaluate)
+
+        self.compiled = None
+        self.recompile()
+
+        btags = self.regexdisplay.bindtags()
+        self.regexdisplay.bindtags(btags[1:] + btags[:1])
+
+        btags = self.stringdisplay.bindtags()
+        self.stringdisplay.bindtags(btags[1:] + btags[:1])
+
+    def addoptions(self):
+        self.frames = []
+        self.boxes = []
+        self.vars = []
+        for name in ('IGNORECASE',
+                     'LOCALE',
+                     'MULTILINE',
+                     'DOTALL',
+                     'VERBOSE'):
+            if len(self.boxes) % 3 == 0:
+                frame = Frame(self.master)
+                frame.pack(fill=X)
+                self.frames.append(frame)
+            val = getattr(re, name)
+            var = IntVar()
+            box = Checkbutton(frame,
+                    variable=var, text=name,
+                    offvalue=0, onvalue=val,
+                    command=self.recompile)
+            box.pack(side=LEFT)
+            self.boxes.append(box)
+            self.vars.append(var)
+
+    def getflags(self):
+        flags = 0
+        for var in self.vars:
+            flags = flags | var.get()
+        flags = flags
+        return flags
+
+    def recompile(self, event=None):
+        try:
+            self.compiled = re.compile(self.regexdisplay.get(),
+                                       self.getflags())
+            bg = self.promptdisplay['background']
+            self.statusdisplay.config(text="", background=bg)
+        except re.error as msg:
+            self.compiled = None
+            self.statusdisplay.config(
+                    text="re.error: %s" % str(msg),
+                    background="red")
+        self.reevaluate()
+
+    def reevaluate(self, event=None):
+        try:
+            self.stringdisplay.tag_remove("hit", "1.0", END)
+        except TclError:
+            pass
+        try:
+            self.stringdisplay.tag_remove("hit0", "1.0", END)
+        except TclError:
+            pass
+        self.grouplist.delete(0, END)
+        if not self.compiled:
+            return
+        self.stringdisplay.tag_configure("hit", background="yellow")
+        self.stringdisplay.tag_configure("hit0", background="orange")
+        text = self.stringdisplay.get("1.0", END)
+        last = 0
+        nmatches = 0
+        while last <= len(text):
+            m = self.compiled.search(text, last)
+            if m is None:
+                break
+            first, last = m.span()
+            if last == first:
+                last = first+1
+                tag = "hit0"
+            else:
+                tag = "hit"
+            pfirst = "1.0 + %d chars" % first
+            plast = "1.0 + %d chars" % last
+            self.stringdisplay.tag_add(tag, pfirst, plast)
+            if nmatches == 0:
+                self.stringdisplay.yview_pickplace(pfirst)
+                groups = list(m.groups())
+                groups.insert(0, m.group())
+                for i in range(len(groups)):
+                    g = "%2d: %r" % (i, groups[i])
+                    self.grouplist.insert(END, g)
+            nmatches = nmatches + 1
+            if self.showvar.get() == "first":
+                break
+
+        if nmatches == 0:
+            self.statusdisplay.config(text="(no match)",
+                                      background="yellow")
+        else:
+            self.statusdisplay.config(text="")
+
+
+# Main function, run when invoked as a stand-alone Python program.
+
+def main():
+    root = Tk()
+    demo = ReDemo(root)
+    root.protocol('WM_DELETE_WINDOW', root.quit)
+    root.mainloop()
+
+if __name__ == '__main__':
+    main()
diff --git a/Tools/demo/rpython.py b/Tools/demo/rpython.py
index e965720..5e7bc0a 100755
--- a/Tools/demo/rpython.py
+++ b/Tools/demo/rpython.py
@@ -1,7 +1,9 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
 
-# Remote python client.
-# Execute Python commands remotely and send output back.
+"""
+Remote python client.
+Execute Python commands remotely and send output back.
+"""
 
 import sys
 from socket import socket, AF_INET, SOCK_STREAM, SHUT_WR
diff --git a/Tools/demo/rpythond.py b/Tools/demo/rpythond.py
index fe24b3d..9ffe13a 100755
--- a/Tools/demo/rpythond.py
+++ b/Tools/demo/rpythond.py
@@ -1,9 +1,12 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
 
-# Remote python server.
-# Execute Python commands remotely and send output back.
-# WARNING: This version has a gaping security hole -- it accepts requests
-# from any host on the Internet!
+"""
+Remote python server.
+Execute Python commands remotely and send output back.
+
+WARNING: This version has a gaping security hole -- it accepts requests
+from any host on the Internet!
+"""
 
 import sys
 from socket import socket, AF_INET, SOCK_STREAM
diff --git a/Tools/demo/sortvisu.py b/Tools/demo/sortvisu.py
index 4173121..8447bc7 100644..100755
--- a/Tools/demo/sortvisu.py
+++ b/Tools/demo/sortvisu.py
@@ -1,6 +1,7 @@
-#! /usr/bin/env python3
+#!/usr/bin/env python3
 
-"""Sorting algorithms visualizer using Tkinter.
+"""
+Sorting algorithms visualizer using Tkinter.
 
 This module is comprised of three ``components'':
 
@@ -15,13 +16,11 @@ to its annotation methods;
 
 - and a ``driver'' class which can be used as a Grail applet or as a
 stand-alone application.
-
 """
 
 from tkinter import *
 import random
 
-
 XGRID = 10
 YGRID = 10
 WIDTH = 6
diff --git a/Tools/demo/ss1.py b/Tools/demo/ss1.py
index 8b07489..2d1e490 100644..100755
--- a/Tools/demo/ss1.py
+++ b/Tools/demo/ss1.py
@@ -1,4 +1,8 @@
-"""SS1 -- a spreadsheet."""
+#!/usr/bin/env python3
+
+"""
+SS1 -- a spreadsheet-like application.
+"""
 
 import os
 import re
diff --git a/Tools/demo/Vec.py b/Tools/demo/vector.py
index 787af69..da5b389 100644..100755
--- a/Tools/demo/Vec.py
+++ b/Tools/demo/vector.py
@@ -1,7 +1,13 @@
+#!/usr/bin/env python3
+
+"""
+A demonstration of classes and their special methods in Python.
+"""
+
 class Vec:
-    """ A simple vector class
+    """A simple vector class.
 
-    Instances of the Vec class  can be constructed from numbers
+    Instances of the Vec class can be constructed from numbers
 
     >>> a = Vec(1, 2, 3)
     >>> b = Vec(3, 2, 1)