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POPython tkinter: plot function with canvas, HOMEWORK
 

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  1. POPython tkinter: plot function with canvas, HOMEWORK
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    <p>An assignment for uni asks me to use tkinter to create a GUI program that takes a function, color, start point, end point and how many steps to take between (line drawn between each step).</p> <p>I have had a decent go at it. I have got the entire layout and frame finished (basically) I am finding a few things a little hard. </p> <p>we have been given this support code.</p> <pre><code>from Tkinter import * import tkMessageBox from tkColorChooser import askcolor from math import * class FunctionError(Exception): """A simple function error exception produced by the make_function function for invalid function definitions. """ pass def make_function(text): """Take a string representing a function in x and return the corresponding function. The FunctionError exception is thrown if text does not represent a valid function. make_function(string) -&gt; (float -&gt; float) """ try: exec 'f = lambda x: ' + text 1+f(2.0) ## test to see if there are any errors in the definition except ZeroDivisionError: ## ignore zero division errors pass except: raise FunctionError() return f class FunctionIterator(object): """An iterator object that is intended to be used to produce (x,y) pairs of a function Constructor: FunctionIterator(function, startx, endx, steps) function is the function being iterated over startx is the x value to start the iteration endx is the x value at the end of the iteration steps is the number of iterations. Assumes if a division by zero occurs at a given x it won't occur 'close to' x Example: Assume square is a function defined to square a number - i.e. square(x) = x*x Then &gt;&gt;&gt; list(FunctionIterator(square, 0.0, 5.0, 5)) [(0.0, 0.0), (1.0, 1.0), (2.0, 4.0), (3.0, 9.0), (4.0, 16.0), (5.0, 25.0)] and for x,y in FunctionIterator(square, 0.0, 5.0, 5): print x,y produces output 0.0 0.0 1.0 1.0 2.0 4.0 3.0 9.0 4.0 16.0 5.0 25.0 NOTE: for functions that are undefined at a given x (e.g. log(-1)) the y value returned is set to 10000000 """ def __init__(self, f, startx, endx, steps): self._f = f self._startx = startx self._endx = endx self._delta = (endx-startx)/steps def __iter__(self): self._x = self._startx self._zero = False return self def next(self): if self._x &gt; self._endx + self._delta/2: raise StopIteration else: x = self._x try: y = self._f(x) self._x += self._delta return (x, y) except ZeroDivisionError: if x == self._startx: x += self._delta/2 y = self._f(x) self._x += self._delta return (x, y) elif self._zero: x += self._delta/2 y = self._f(x) self._x += self._delta self._zero = False return (x, y) else: x -= self._delta/2 y = self._f(x) self._zero = True return (x, y) except: self._x += self._delta return (x, 10000000) class WorldScreen(object): """The WorldScreen class is used to convert between real coodinates and screen coordinates. Constructor: WorldScreen(x1, y1, x2, y2, width, height) (x1, y1) : The bottom left in real coords (x2, y2) : The top right in real coords width : the width of the screen (canvas) height: the height of the screen (canvas) NOTE: On a canvas the y increases are you move down the canvas so a 'flip' occurs between real y values and screen values - see example below """ def __init__(self, x1, y1, x2, y2, width, height): self.x = x1 self.y = y1 self.xscale = (x2-x1)/width self.yscale = (y2-y1)/height self.height = height def world2screen(self, x, y): """Return the screen (canvas) coordinates given real coordinates. If the calculated screen y coord is outside the screen then the appropriate 'edge value' is returned. world2screen(float, float) -&gt; (float, float) Example: &gt;&gt;&gt; ws = World_Screen(0,0,10,10, 100.0, 100.0) &gt;&gt;&gt; ws.world2screen(5, 5) (50.0, 50.0) &gt;&gt;&gt; ws.world2screen(10, 10) (100.0, 0.0) Note that in this case when y is 10 in real coordinates (i.e. at the top then the y coord in the canvas is 0 (i.e. at the top) """ wy = self.height - (y - self.y)/self.yscale """ if wy &lt; 0: wy = 0 elif wy &gt; self.height: wy = self.height """ return ((x-self.x)/self.xscale, wy) def screen2world(self, x, y): """Return the real coordinates given screen (canvas)coordinates. screen2world(float, float) -&gt; (float, float) Example: &gt;&gt;&gt; ws = World_Screen(0,0,10,10, 100.0, 100.0) &gt;&gt;&gt; ws.screen2world(50,50) (5.0, 5.0) &gt;&gt;&gt; ws.screen2world(100,0) (10.0, 10.0) """ return (x*self.xscale + self.x, (self.height - y)*self.yscale + self.y) </code></pre> <p>This is my code</p> <pre><code>class PointFrame(Frame): """a simple application to allow a user ti enter an expression and evaluate it """ def __init__(self, master): """ a a=simple expression evaluator """ Frame.__init__(self, master) Label(self, text='Last Point Clicked: ').pack(side=LEFT) Label(self, text='').pack(side=LEFT) Label(self, text='Cursor Point: ').pack(side=LEFT) Label(self, text='').pack(side=LEFT) class CanvasApp(object): def __init__(self, master): master.title('canvas') self._canvas = Canvas(master, bg='white', width=500, height=500) self._canvas.pack(side=TOP, expand=True, fill=BOTH) class FunctionFrame(Frame): """a simple application to allow a user ti enter an expressio n and evaluate it """ def __init__(self, master): """ a a=simple expression evaluator """ Frame.__init__(self, master, relief=SUNKEN, bg='#A5A5A5', pady=3) Label(self, text='Function in x: ', bg='#A5A5A5').pack(side=LEFT) function = Entry(self, width=35).pack(side=LEFT, padx=2) Button(self, text='Select', command=self.select).pack(side=RIGHT, padx=4) colour = Entry(self, width=15).pack(side=RIGHT) Label(self, text='Function Colour: ', bg='#A5A5A5').pack(side=RIGHT, padx=2) def select(self): (rgb, hx)= askcolor() class PlotFrame(Frame): """a simple application to allow a user ti enter an expression and evaluate it """ def __init__(self, master): """ a a=simple expression evaluator """ entry_width = 10 Frame.__init__(self, master, bg='#A5A5A5', pady=3) Label(self, text='Plot Settings', bg='#A5A5A5').pack(side=LEFT) Label(self, text='Start X:', bg='#A5A5A5').pack(side=LEFT) start_x = Entry(self, width=entry_width).pack(side=LEFT) Label(self, text='End X:', bg='#A5A5A5').pack(side=LEFT) end_x = Entry(self, width=entry_width).pack(side=LEFT) Label(self, text='Start Y:', bg='#A5A5A5').pack(side=LEFT) start_y = Entry(self, width=entry_width).pack(side=LEFT) Label(self, text='End Y:', bg='#A5A5A5').pack(side=LEFT) end_y = Entry(self, width=entry_width).pack(side=LEFT) Label(self, text='Steps: ', bg='#A5A5A5').pack(side=LEFT) steps = Entry(self, width=entry_width).pack(side=LEFT) class ButtonFrame(Frame): """a simple application to allow a user ti enter an expression and evaluate it """ def __init__(self, master): """ a a=simple expression evaluator """ Frame.__init__(self, master, bg='#CECEF6') Button(self, text='Add Function', command=self.add_function).pack(side=LEFT) Button(self, text='Redraw All', command=self.redraw_all).pack(side=LEFT) Button(self, text='Remove Last Function', command=self.remove_last).pack(side=LEFT) Button(self, text='Remove All Functions', command=self.remove_all).pack(side=LEFT) Button(self, text='Exit', command=self.exit_app).pack(side=LEFT) def add_function(self): make_function(function) def redraw_all(self): pass def remove_last(self): pass def remove_all(self): pass def exit_app(self): self.master.destroy class PlotApp(object): def __init__(self, master): master.title('Assignment 2') PointFrame(master).pack(side=TOP, expand=True, fill=BOTH, pady=2) self._canvas = Canvas(master, bg='white', width=500, height=500).pack(side=TOP, expand=True, fill=BOTH, padx=8) FunctionFrame(master).pack(side=TOP, expand=True, fill=BOTH, pady=4) separator = Frame(height=18, bd=1) separator.pack(fill=X) PlotFrame(master).pack(side=TOP, expand=True, fill=BOTH, pady=4) separator = Frame(height=10, bd=1) separator.pack(fill=X) ButtonFrame(master).pack(side=TOP, pady=5) </code></pre> <p>The things im having problems with;</p> <ol> <li><p>How can i use the make_function function in the support code to check if the function given in my entry (function) is a function. Sorry for saying function so much.</p></li> <li><p>my first class - pointframe is meant o show the last clicked point in the canval and current curser point in real world coordinates. I am meant to use the worldscreen function in the support to convert into real world cords. How can i do this?</p></li> <li><p>the select button uses tkcolorchooser to pick a color. how can i make that color come up in the color entry next to it?</p></li> <li><p>how can i use the color, function, start and end point and steps to draw a function. using the functioniterator in the support code? then how can i draw over it with a new one, change color, delete all and redraw all?</p></li> </ol> <p>I realize this is alot. i am not asking for someone to just do it for me. I am just after helps, hints and anything that can help me get closer.</p> <p>Thank you</p>
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      1. POPython tkinter: plot function with canvas, HOMEWORK
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      1. POPython tkinter: plot function with canvas, HOMEWORK
      1. USJustin S Barrett
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    1. COYou say that you don't want someone to just do it for you, and yet your questions appear (to me, at least) to be very broad -- especially #4 -- and you haven't told us what you've already done to try and solve each of those problems. If you *have* tried things and they haven't worked, please update your original question with details about what you tried and why it failed. I also suggest submitting each problem as a separate question (once you've tried to solve it yourself), rather than lumping all four questions into one request for help.
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      1. USJustin S Barrett
 

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