User Interfaces. getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy

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1 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget MCS 507 Lecture 11 Mathematical, Statistical and Scientific Software Jan Verschelde, 20 September 2013 Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

2 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

3 command line interfaces Many programs run without dialogue with user, as $ executable -options inputfile outputfile Command line arguments are useful for changing default values of parameters; running program in special mode, e.g.: python -O turns on basic optimization; without delaying for typed user input, we can use the time command of the operating system. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

4 print command line arguments To get the command line arguments into Python: import sys L = sys.argv print the list of arguments : print L print number of arguments :, len(l) for k in xrange(len(l)): print argument %d is %s % (k, L[k]) Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

5 running show_cmdlinargs.py $ python show_cmdlinargs.py a 3.14 the list of arguments : [ show_cmdlinargs.py, a, 3.14 ] number of arguments : 3 argument 0 is show_cmdlinargs.py argument 1 is a argument 2 is 3.14 The arguments given at the command line are strings. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

6 executing Python scripts If the file hello_python.py contains #! /usr/bin/python print welcome to Python then we can run the script at the prompt $ as $./hello_python.py welcome to Python The script starts with the location of the interpreter. Do which python to find location of python. Eventually, do chmod +x hello_python.py. Possible to run script by clicking on its icon. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

7 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

8 storing data points Suppose we want to store points (x, y) permanently. Running our script storepoints.py as $./storepoints.py db=data -a 1,2 adding 1 2 $./storepoints.py db=data -v 1 value of 1 is 2 $./storepoints.py db=data -L (1,2) respectively adds (1,2), gets the value of 1, and lists all points stored in the anydbm file data. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

9 a top down design Starting at the top we apply stepwise refinement of the main program: 1 open the database, 2 decode the command line options, 3 for valid options, perform the action. The sequence of three steps in the main program is defined by the following subroutines: 1 open the database (anydbm object), 2 extract the option of a command line argument, 3 handle a valid option with 3 subroutines: 1 adding a point (x,y), 2 given x, get the corresponding y, 3 list all points. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

10 the main program def main(): Opens database and handles options. import sys cmdargs = sys.argv adb = open_database(cmdargs) if adb == None: print opening of database failed else: option = extract_option(cmdargs) if option == None: print no valid option found else: handle(adb, option) if name == " main ": main() Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

11 opening the database def open_database(cmdlist): Extracts the database name from the list of command line arguments. If the database could be opened, then it is returned, otherwise None is returned. for item in cmdlist: items = item.split( = ) if len(items) == 2: try: adb = anydbm.open(items[1], c ) print opening, items[1], succeeded return adb except: print opening, items[1], failed return None return None Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

12 extracting options def extract_option(cmdlist): Returns a tuple with the option letter and the data following the option. for k in xrange(len(cmdlist)): item = cmdlist[k] if item[0] == - : if item[1] == L : return ( L, None) try: return (item[1], cmdlist[k+1]) except: print no data with option, item[1] return None return None Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

13 handling options def handle(adb, opt): Given in opt a tuple of option letter and argument, adds a point, returns a value, or prints an error message. if opt[0] == a : add_point(adb, opt[1]) elif opt[0] == v : value_of_point(adb, opt[1]) elif opt[0] == L : list_points(adb) else: print opt[0], is invalid option Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

14 adding points def add_point(adb, inpstr): Adds the point in the string inpstr encoded as x,y. coords = inpstr.split(, ) (ptx, pty) = tuple(coords) print adding, ptx, pty adb[ptx] = pty Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

15 getting values def value_of_point(adb, inpstr): Prints the value of the point with key stored in the string inpstr. if adb.has_key(inpstr): print value of, inpstr, is, adb[inpstr] else: print inpstr, has no value def list_points(adb): Shows the list of points stored in adb. for key in adb.keys(): print ( + key +, + adb[key] + ) Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

16 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

17 using numpy.polyfit >>> import numpy as np >>> x = np.array([-1,0,1]) >>> y = np.array([2,0,3]) >>> p = np.polyfit(x,y,deg=2) >>> p array([ e+00, e-01, e-16]) >>> z = np.polyval(p,x) >>> z array([ e+00, e-16, e+00]) numpy.polyfit fits a set of points with a polynomial of a given degree, solving a least squares problem with a singular value decomposition. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

18 visualization with ipython Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

19 session with ipython $ ipython --pylab In [1]: x = array([-1,0,1]); y = array([2,0,3]) In [2]: p = polyfit(x,y,deg=2) In [3]: r = arange(-1.5,1.5,0.01) In [4]: rp = polyval(p,r) In [5]: plot(x,y, rd ) Out[5]: [<matplotlib.lines.line2d at 0x1068f6110>] In [6]: plot(r,rp, b- ) Out[6]: [<matplotlib.lines.line2d at 0x d0>] Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

20 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

21 Object Oriented Design Top down design works well for precisely defined programs but requirements in programs often change and bugs arise. The main object is a collection of tuples (x,y) stored in a database. To the user, the data (x,y) are just points. In an object oriented design, we have an object points. Encapsulation is also an interface. We will refactor the top down code into a class. Object oriented design works from the bottom up: we can test the operations on the points collection without a main program. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

22 defining a class The class defines an interface to an anydbm object: 1 Given a name of a database, the initialization creates a new or opens an existing database. 2 The string representation returns the list of points stored in the database. 3 The two other method are 1 add a point (x,y), 2 given x, return y. Encapsulation: the user of the class does not see anydbm. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

23 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

24 an interactive test In the Python shell: >>> from classpointsdb import * >>> p = Points("data") opening data succeeded >>> p.add_point("1,2") adding 1 2 >>> print str(p) (1,2) >>> p.value_of_point("1") 2 Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

25 the constructor of the class import anydbm class Points(object): Encapsulation of an anydbm object to store a collection of coordinates of points in the plane. def init (self, name): Attempts to open the database with the name. try: self.adb = anydbm.open(name, c ) print opening, name, succeeded except: print opening, name, failed self.adb = None Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

26 the string representation def str (self): Shows the list of stored points. keys = self.adb.keys() result = "" for k in keys: result += ( + k +, + self.adb[k] + ) return result Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

27 adding a point def add_point(self, inpstr): Adds the point in the string inpstr encoded as x, y. coords = inpstr.split(, ) (ptx, pty) = tuple(coords) print adding, ptx, pty self.adb[ptx] = pty Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

28 getting the value of a point def value_of_point(self, inpstr): Returns the value of the point with key stored in the string inpstr if self.adb.has_key(inpstr): return self.adb[inpstr] else: return None Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

29 the test program def test(): Tests the methods of the Points class. pts = Points("data") pts.add_point("1,2") print str(pts) print "the value of 1 is", pts.value_of_point("1") if name == " main ": test() Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

30 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

31 Tkinter, Tk, and Tcl The Tkinter (= Tk interface) library provides an object-oriented interface to the Tk GUI toolkit, the graphical interface development tool for Tcl, Tk = Tool Kit, Tcl = Tool Command Language. Benefit: platform independent GUI development. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

32 User Interfaces 1 Command Line Interfaces getting arguments of the command line a command line interface to store points fitting points with polyfit of numpy 2 Encapsulation by Object Oriented Programming an interface to an anydbm object refactoring a script into a class 3 The Tk GUI Toolkit in Python Tkinter, Tk, and Tcl using the canvas widget Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

33 five points on canvas Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

34 computing the coordinates from Tkinter import Tk, Canvas from math import cos, sin, pi D = 400 # number of pixels in rows/columns R = 0.8*D/2 # radius of the pentagon A = 2*pi/5 # dividing angle L = [(D/2, D/2-R), \ (D/2+R*cos(pi/2-A), D/2-R*sin(pi/2-A)), \ (D/2+R*cos(pi/2-2*A), D/2-R*sin(pi/2-2*A)), \ (D/2+R*cos(pi/2-3*A), D/2-R*sin(pi/2-3*A)), \ (D/2+R*cos(pi/2-4*A), D/2-R*sin(pi/2-4*A))] Note that the origin (0, 0) is at the topleft corner. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

35 a canvas widget We define a new window and title. The method pack() arranges the canvas in the window. WDW = Tk() WDW.title( five points ) C = Canvas(WDW, width=d, height=d, bg= white ) C.pack() for p in L: C.create_oval(p[0]-6, p[1]-6, p[0]+6, p[1]+6, \ width=1, outline= black, fill= SkyBlue2 ) The points are marked on canvas by blue disks. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

36 fitting the points Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

37 applying polyfit import numpy as np A = np.array([x for (x, y) in L]) B = np.array([y for (x, y) in L]) QUARTIC = np.polyfit(a, B, 4) for i in xrange(400): j = np.polyval(quartic, i) C.create_oval(i-1, j-1, i+1, j+1, \ width=1, outline= red, fill= red ) WDW.mainloop() Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

38 Summary + Exercises Command line arguments are passed as strings to a Python script. We make GUIs with TKinter (continued on Monday). Exercises: 1 Extend storepoints.py with an option -d x to delete points with given x value 2 Add an exception handler to the function add_point for when the comma is missing or the coordinates fail to convert to floats. 3 Modify the code for -v x of storepoints.py so that it returns the value of a quadratic fit in case the value for the given x is not stored. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39

39 more exercises 4 Change the pentagon.py script so that it gets its points from an anydbm file made with storepoints.py. 5 Use the code in pentagon.py as a visualization module for storepoints.py. With the option -s a canvas window pops up displaying the stored points. The first project is due on Wednesday 2 October, at 9AM. Scientific Software (MCS 507 L-11) user interfaces 20 September / 39