Hello,
This is one of the questions in Python Programming by Zelle. Ch 5, #1b.
The problem calls for the program to create a new square at the mouse
click instead of moving the square as in the previous problem.
I have tried various ways to tackle the problem with no success. Any
help would be greatly be appreciated.
This is the code that works for the previous example and moved the
square at the mouse click:
------
# Modify the example in the book to program to draw a square instead
of a circle.
# Interactive graphics program to draw a square
from graphics import *
def main():
win = GraphWin()
shape = Rectangle(Point(50,50), Point(20,20))
shape.setOutline("red")
shape.setFill("red")
shape.draw(win)
for i in range(10):
p = win.getMouse()
c = shape.getCenter()
dx = p.getX() - c.getX()
dy = p.getY() - c.getY()
shape.move(dx,dy)
win.close()
main()
#This one worked without too much trouble. All I had to do was change
the object to be
# drawn to a square!
--------------------------
This is the mess i got myself into with the next problem. Please note
that I initially tried to move the shape.draw(win) object to the
beginning of the loop and I got an error that said:
Traceback (most recent call last):
File "/Users/krissd/Desktop/python/code_zelle/chapter5/1a.py",
line 21, in <module>
main()
File "/Users/krissd/Desktop/python/code_zelle/chapter5/1a.py",
line 14, in main
shape.draw(win)
File "/Users/krissd/Desktop/python/code_zelle/chapter5/
graphics.py", line 280, in draw
if self.canvas: raise GraphicsError, OBJ_ALREADY_DRAWN
graphics.GraphicsError: ('O', 'b', 'j', 'e', 'c', 't', ' ', 'c', 'u',
'r', 'r', 'e', 'n', 't', 'l', 'y', ' ', 'd', 'r', 'a', 'w', 'n')
230-152:~/Desktop/python/code_zelle/chapter5 krissd$
Second program:
This one draws squares, but not of the same dimensions as the first
and not with the center at the mouse click.
---------------------
# Modify the example in the book to program to draw a square instead
of a circle.
# Additionally, have a new square drawn each time the mouse is clicked.
from graphics import *
def main():
win = GraphWin()
shape = Rectangle(Point(50,50), Point(20,20))
shape.setOutline("red")
shape.setFill("red")
shape.draw(win)
for i in range(10): gui
p = win.getMouse()
c = shape.getCenter()
dx = p.getX() # - c.getX()
dy = p.getY() # - c.getY()
shape = Rectangle(Point(dx,dx),Point(dy,dy))
shape.setOutline("red")
shape.setFill("red")
shape.draw(win)
win.close()
main()
#This is turning out trickier than I thought!
# I have gotten close. It redraws the square, but not with the same
dimensions
# at a different location determined by the mouse click.
# I am barking up the wrong tree with this effort!!!!
----------------
I have attached the graphics package that is used in the program for
reference.# graphics.py
"""Simple object oriented graphics library
The library is designed to make it very easy for novice programmers to
experiment with computer graphics in an object oriented fashion. It is
written by John Zelle for use with the book "Python Programming: An
Introduction to Computer Science" (Franklin, Beedle & Associates).
LICENSE: This is open-source software released under the terms of the
GPL (http://www.gnu.org/licenses/gpl.html).
PLATFORMS: The package is a wrapper around Tkinter and should run on
any platform where Tkinter is available.
INSTALLATION: Put this file somewhere where Python can see it.
OVERVIEW: There are two kinds of objects in the library. The GraphWin
class implements a window where drawing can be done, and various
GraphicsObjects are provided that can be drawn into a GraphWin. As a
simple example, here is a complete program to draw a circle of radius
10 centered in a 100x100 window:
--------------------------------------------------------------------
from graphics import *
def main():
win = GraphWin("My Circle", 100, 100)
c = Circle(Point(50,50), 10)
c.draw(win)
main()
--------------------------------------------------------------------
GraphWin objects support coordinate transformation through the
setCoords method and pointer-based input through getMouse.
The library provides the following graphical objects:
Point
Line
Circle
Oval
Rectangle
Polygon
Text
Entry (for text-based input)
Image
Various attributes of graphical objects can be set such as
outline-color, fill-color and line-width. Graphical objects also
support moving and hiding for animation effects.
DOCUMENTATION: For complete documentation, see Chapter 5 of "Python
Programming: An Introduction to Computer Science" by John Zelle,
published by Franklin, Beedle & Associates. """
# Version 2.0
# Updated Documentation
# Made Polygon accept a list of Points in constructor
# Made all drawing functions call TK update for easier animations
# and to make the overall package work better with
# Python 2.3 and IDLE 1.0 under Windows (still some issues).
# Removed vestigial turtle graphics.
# Added ability to configure font for Entry objects (analogous to Text)
# Added setTextColor for Text as an alias of setFill
# Changed to class-style exceptions
# Fixed cloning of Text objects
# Version 1.6
# Fixed Entry so StringVar uses _root as master, solves weird
# interaction with shell in Idle
# Fixed bug in setCoords. X and Y coordinates can increase in
# "non-intuitive" direction.
# Tweaked wm_protocol so window is not resizable and kill box closes.
# Version 1.5
# Fixed bug in Entry. Can now define entry before creating a
# GraphWin. All GraphWins are now toplevel windows and share
# a fixed root (called _root).
# Version 1.4
# Fix Garbage collection of Tkinter images bug.
# Add ability to set text atttributes.
# Add Entry boxes.
import Tkinter
tk = Tkinter
from copy import copy
import exceptions
class GraphicsError(exceptions.Exception):
"""Generic error class for graphics module exceptions."""
def __init__(self, args=None):
self.args=args
OBJ_ALREADY_DRAWN = "Object currently drawn"
UNSUPPORTED_METHOD = "Object doesn't support operation"
BAD_OPTION = "Illegal option value"
# create an invisible global main root for all windows
_root = tk.Tk()
_root.withdraw()
class GraphWin(tk.Canvas):
"""A GraphWin is a toplevel window for displaying graphics."""
def __init__(self, title="Graphics Window", width=200, height=200):
master = tk.Toplevel(_root)
master.protocol("WM_DELETE_WINDOW", self.close)
tk.Canvas.__init__(self, master, width=width, height=height)
self.master.title(title)
self.pack()
master.resizable(0,0)
self.foreground = "black"
self.items = []
self.mouseX = None
self.mouseY = None
self.bind("<Button-1>", self._onClick)
self.height = height
self.width = width
self._mouseCallback = None
self.trans = None
_root.update()
def setBackground(self, color):
"""Set background color of the window"""
self.config(bg=color)
def setCoords(self, x1, y1, x2, y2):
"""Set coordinates of window to run from (x1,y1) in the
lower-left corner to (x2,y2) in the upper-right corner."""
self.trans = Transform(self.width, self.height, x1, y1, x2, y2)
def close(self):
"""Close the window"""
self.master.destroy()
self.quit()
_root.update()
def plot(self, x, y, color="black"):
"""Set pixel (x,y) to the given color"""
xs,ys = self.toScreen(x,y)
self.create_line(xs,ys,xs+1,ys, fill=color)
_root.update()
def plotPixel(self, x, y, color="black"):
"""Set pixel raw (independent of window coordinates) pixel
(x,y) to color"""
self.create_line(x,y,x+1,y, fill=color)
_root.update()
def flush(self):
"""Update drawing to the window (deprecated)"""
self.update_idletasks()
def getMouse(self):
"""Wait for mouse click and return Point object representing
the click"""
self.mouseX = None
self.mouseY = None
while self.mouseX == None or self.mouseY == None:
self.update()
x,y = self.toWorld(self.mouseX, self.mouseY)
return Point(x,y)
def getHeight(self):
"""Return the height of the window"""
return self.height
def getWidth(self):
"""Return the width of the window"""
return self.width
def toScreen(self, x, y):
trans = self.trans
if trans:
return self.trans.screen(x,y)
else:
return x,y
def toWorld(self, x, y):
trans = self.trans
if trans:
return self.trans.world(x,y)
else:
return x,y
def setMouseHandler(self, func):
self._mouseCallback = func
def _onClick(self, e):
self.mouseX = e.x
self.mouseY = e.y
if self._mouseCallback:
self._mouseCallback(Point(e.x, e.y))
class Transform:
"""Internal class for 2-D coordinate transformations"""
def __init__(self, w, h, xlow, ylow, xhigh, yhigh):
# w, h are width and height of window
# (xlow,ylow) coordinates of lower-left [raw (0,h-1)]
# (xhigh,yhigh) coordinates of upper-right [raw (w-1,0)]
xspan = (xhigh-xlow)
yspan = (yhigh-ylow)
self.xbase = xlow
self.ybase = yhigh
self.xscale = xspan/float(w-1)
self.yscale = yspan/float(h-1)
def screen(self,x,y):
# Returns x,y in screen (actually window) coordinates
xs = (x-self.xbase) / self.xscale
ys = (self.ybase-y) / self.yscale
return int(xs+0.5),int(ys+0.5)
def world(self,xs,ys):
# Returns xs,ys in world coordinates
x = xs*self.xscale + self.xbase
y = self.ybase - ys*self.yscale
return x,y
# Default values for various item configuration options. Only a subset of
# keys may be present in the configuration dictionary for a given item
DEFAULT_CONFIG = {"fill":"",
"outline":"black",
"width":"1",
"arrow":"none",
"text":"",
"justify":"center",
"font": ("helvetica", 12, "normal")}
class GraphicsObject:
"""Generic base class for all of the drawable objects"""
# A subclass of GraphicsObject should override _draw and
# and _move methods.
def __init__(self, options):
# options is a list of strings indicating which options are
# legal for this object.
# When an object is drawn, canvas is set to the GraphWin(canvas)
# object where it is drawn and id is the TK identifier of the
# drawn shape.
self.canvas = None
self.id = None
# config is the dictionary of configuration options for the widget.
config = {}
for option in options:
config[option] = DEFAULT_CONFIG[option]
self.config = config
def setFill(self, color):
"""Set interior color to color"""
self._reconfig("fill", color)
def setOutline(self, color):
"""Set outline color to color"""
self._reconfig("outline", color)
def setWidth(self, width):
"""Set line weight to width"""
self._reconfig("width", width)
def draw(self, graphwin):
"""Draw the object in graphwin, which should be a GraphWin
object. A GraphicsObject may only be drawn into one
window. Raises an error if attempt made to draw an object that
is already visible."""
if self.canvas: raise GraphicsError, OBJ_ALREADY_DRAWN
self.canvas=graphwin
self.id = self._draw(graphwin, self.config)
_root.update()
def undraw(self):
"""Undraw the object (i.e. hide it). Returns silently if the
object is not currently drawn."""
if not self.canvas: return
self.canvas.delete(self.id)
self.canvas = None
self.id = None
_root.update()
def move(self, dx, dy):
"""move object dx units in x direction and dy units in y
direction"""
self._move(dx,dy)
canvas = self.canvas
if canvas:
trans = canvas.trans
if trans:
x = dx/ trans.xscale
y = -dy / trans.yscale
else:
x = dx
y = dy
self.canvas.move(self.id, x, y)
_root.update()
def _reconfig(self, option, setting):
# Internal method for changing configuration of the object
# Raises an error if the option does not exist in the config
# dictionary for this object
if not self.config.has_key(option):
raise GraphicsError, UNSUPPORTED_METHOD
options = self.config
options[option] = setting
if self.canvas: self.canvas.itemconfig(self.id, options)
_root.update()
def _draw(self, canvas, options):
"""draws appropriate figure on canvas with options provided
Returns Tk id of item drawn"""
pass # must override in subclass
def _move(self, dx, dy):
"""updates internal state of object to move it dx,dy units"""
pass # must override in subclass
class Point(GraphicsObject):
def __init__(self, x, y):
GraphicsObject.__init__(self, ["outline", "fill"])
self.setFill = self.setOutline
self.x = x
self.y = y
def _draw(self, canvas, options):
x,y = canvas.toScreen(self.x,self.y)
return canvas.create_rectangle(x,y,x+1,y+1,options)
def _move(self, dx, dy):
self.x = self.x + dx
self.y = self.y + dy
def clone(self):
other = Point(self.x,self.y)
other.config = self.config
return other
def getX(self): return self.x
def getY(self): return self.y
class _BBox(GraphicsObject):
# Internal base class for objects represented by bounding box
# (opposite corners) Line segment is a degenerate case.
def __init__(self, p1, p2, options=["outline","width","fill"]):
GraphicsObject.__init__(self, options)
self.p1 = p1.clone()
self.p2 = p2.clone()
def _move(self, dx, dy):
self.p1.x = self.p1.x + dx
self.p1.y = self.p1.y + dy
self.p2.x = self.p2.x + dx
self.p2.y = self.p2.y + dy
def getP1(self): return self.p1
def getP2(self): return self.p2
def getCenter(self):
p1 = self.p1
p2 = self.p2
return Point((p1.x+p2.x)/2.0, (p1.y+p2.y)/2.0)
class Rectangle(_BBox):
def __init__(self, p1, p2):
_BBox.__init__(self, p1, p2)
def _draw(self, canvas, options):
p1 = self.p1
p2 = self.p2
x1,y1 = canvas.toScreen(p1.x,p1.y)
x2,y2 = canvas.toScreen(p2.x,p2.y)
return canvas.create_rectangle(x1,y1,x2,y2,options)
def clone(self):
other = Rectangle(self.p1, self.p2)
other.config = self.config
return other
class Oval(_BBox):
def __init__(self, p1, p2):
_BBox.__init__(self, p1, p2)
def clone(self):
other = Oval(self.p1, self.p2)
other.config = self.config
return other
def _draw(self, canvas, options):
p1 = self.p1
p2 = self.p2
x1,y1 = canvas.toScreen(p1.x,p1.y)
x2,y2 = canvas.toScreen(p2.x,p2.y)
return canvas.create_oval(x1,y1,x2,y2,options)
class Circle(Oval):
def __init__(self, center, radius):
p1 = Point(center.x-radius, center.y-radius)
p2 = Point(center.x+radius, center.y+radius)
Oval.__init__(self, p1, p2)
self.radius = radius
def clone(self):
other = Circle(self.getCenter(), self.radius)
other.config = self.config
return other
def getRadius(self):
return self.radius
class Line(_BBox):
def __init__(self, p1, p2):
_BBox.__init__(self, p1, p2, ["arrow","fill","width"])
self.setFill(DEFAULT_CONFIG['outline'])
self.setOutline = self.setFill
def clone(self):
other = Line(self.p1, self.p2)
other.config = self.config
return other
def _draw(self, canvas, options):
p1 = self.p1
p2 = self.p2
x1,y1 = canvas.toScreen(p1.x,p1.y)
x2,y2 = canvas.toScreen(p2.x,p2.y)
return canvas.create_line(x1,y1,x2,y2,options)
def setArrow(self, option):
if not option in ["first","last","both","none"]:
raise GraphicsError, BAD_OPTION
self._reconfig("arrow", option)
class Polygon(GraphicsObject):
def __init__(self, *points):
# if points passed as a list, extract it
if len(points) == 1 and type(points[0] == type([])):
points = points[0]
self.points = map(Point.clone, points)
GraphicsObject.__init__(self, ["outline", "width", "fill"])
def clone(self):
other = apply(Polygon, self.points)
other.config = self.config
return other
def getPoints(self):
return map(Point.clone, self.points)
def _move(self, dx, dy):
for p in self.points:
p.move(dx,dy)
def _draw(self, canvas, options):
args = [canvas]
for p in self.points:
x,y = canvas.toScreen(p.x,p.y)
args.append(x)
args.append(y)
args.append(options)
return apply(GraphWin.create_polygon, args)
class Text(GraphicsObject):
def __init__(self, p, text):
GraphicsObject.__init__(self, ["justify","fill","text","font"])
self.setText(text)
self.anchor = p.clone()
self.setFill(DEFAULT_CONFIG['outline'])
self.setOutline = self.setFill
def _draw(self, canvas, options):
p = self.anchor
x,y = canvas.toScreen(p.x,p.y)
return canvas.create_text(x,y,options)
def _move(self, dx, dy):
self.anchor.move(dx,dy)
def clone(self):
other = Text(self.anchor, self.config['text'])
other.config = self.config
return other
def setText(self,text):
self._reconfig("text", text)
def getText(self):
return self.config["text"]
def getAnchor(self):
return self.anchor.clone()
def setFace(self, face):
if face in ['helvetica','arial','courier','times roman']:
f,s,b = self.config['font']
self._reconfig("font",(face,s,b))
else:
raise GraphicsError, BAD_OPTION
def setSize(self, size):
if 5 <= size <= 36:
f,s,b = self.config['font']
self._reconfig("font", (f,size,b))
else:
raise GraphicsError, BAD_OPTION
def setStyle(self, style):
if style in ['bold','normal','italic', 'bold italic']:
f,s,b = self.config['font']
self._reconfig("font", (f,s,style))
else:
raise GraphicsError, BAD_OPTION
def setTextColor(self, color):
self.setFill(color)
class Entry(GraphicsObject):
def __init__(self, p, width):
GraphicsObject.__init__(self, [])
self.anchor = p.clone()
#print self.anchor
self.width = width
self.text = tk.StringVar(_root)
self.text.set("")
self.fill = "gray"
self.color = "black"
self.font = DEFAULT_CONFIG['font']
self.entry = None
def _draw(self, canvas, options):
p = self.anchor
x,y = canvas.toScreen(p.x,p.y)
frm = tk.Frame(canvas.master)
self.entry = tk.Entry(frm,
width=self.width,
textvariable=self.text,
bg = self.fill,
fg = self.color,
font=self.font)
self.entry.pack()
self.setFill(self.fill)
return canvas.create_window(x,y,window=frm)
def getText(self):
return self.text.get()
def _move(self, dx, dy):
self.anchor.move(dx,dy)
def getAnchor(self):
return self.anchor.clone()
def clone(self):
other = Entry(self.anchor, self.width)
other.config = self.config
other.text = tk.StringVar()
other.text.set(self.text.get())
other.fill = self.fill
return other
def setText(self, t):
self.text.set(t)
def setFill(self, color):
self.fill = color
if self.entry:
self.entry.config(bg=color)
def _setFontComponent(self, which, value):
font = list(self.font)
font[which] = value
self.font = tuple(font)
if self.entry:
self.entry.config(font=self.font)
def setFace(self, face):
if face in ['helvetica','arial','courier','times roman']:
self._setFontComponent(0, face)
else:
raise GraphicsError, BAD_OPTION
def setSize(self, size):
if 5 <= size <= 36:
self._setFontComponent(1,size)
else:
raise GraphicsError, BAD_OPTION
def setStyle(self, style):
if style in ['bold','normal','italic', 'bold italic']:
self._setFontComponent(2,style)
else:
raise GraphicsError, BAD_OPTION
def setTextColor(self, color):
self.color=color
if self.entry:
self.entry.config(fg=color)
class Image(GraphicsObject):
idCount = 0
imageCache = {} # keep images here to avoid gc
def __init__(self, p, file=None):
GraphicsObject.__init__(self, [])
self.file = file
self.anchor = p.clone()
self.imageId = Image.idCount
Image.idCount = Image.idCount + 1
def _draw(self, canvas, options):
p = self.anchor
x,y = canvas.toScreen(p.x,p.y)
img = tk.PhotoImage(file=self.file, master=canvas)
self.imageCache[self.imageId] = img # save in cache to avoid gc
return canvas.create_image(x,y,image=img)
def _move(self, dx, dy):
self.anchor.move(dx,dy)
def undraw(self):
del self.imageCache[self.imageId] # allow gc of tk photoimage
GraphicsObject.undraw(self)
def getAnchor(self):
return self.anchor.clone()
def clone(self):
other = Image(self.anchor, self.file)
other.config = self.config
return other
def color_rgb(r,g,b):
"""r,g,b are intensities of red, green, and blue in range (0-255)
Returns color specifier string for the resulting color"""
return "#%02x%02x%02x" % (r,g,b)
def test():
win = GraphWin()
win.setCoords(0,0,10,10)
t = Text(Point(5,5), "Centered Text")
t.draw(win)
p = Polygon(Point(1,1), Point(5,3), Point(2,7))
p.draw(win)
e = Entry(Point(5,6), 10)
e.draw(win)
win.getMouse()
p.setFill("red")
p.setOutline("blue")
p.setWidth(2)
s = ""
for pt in p.getPoints():
s = s + "(%0.1f,%0.1f) " % (pt.getX(), pt.getY())
t.setText(e.getText())
e.setFill("green")
e.setText("Spam!")
e.move(2,0)
win.getMouse()
p.move(2,3)
s = ""
for pt in p.getPoints():
s = s + "(%0.1f,%0.1f) " % (pt.getX(), pt.getY())
t.setText(s)
win.getMouse()
p.undraw()
e.undraw()
t.setStyle("bold")
win.getMouse()
t.setStyle("normal")
win.getMouse()
t.setStyle("italic")
win.getMouse()
t.setStyle("bold italic")
win.getMouse()
t.setSize(14)
win.getMouse()
t.setFace("arial")
t.setSize(20)
win.getMouse()
win.close()
if __name__ == "__main__":
test()
One additional question. Zelle creates this graphics library to use
to demonstrate GUI programming. I have seen discussions about tkinter
and wxpython. Should I be trying to use one of them instead for these
problems? Or would that be jumping ahead of the game?
Regards,
kristinn
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