VIII a) . Analysis of ValueSelected.py & Use of Tkinter to make Combo Box
This Wiki Section is designed to explain the code in the file -ValueSelected.py
Tkinter is used as the Python GUI toolkit in our code. Tk is an open source multiplatform widget toolkit that is used by many different languages for building GUI Program.Tkinter interface is implemented as a Python module which is just a wrapper around a C extension that uses Tcl/Tk libraries. How to install Tkinter in Python? Press open your terminal using Ctrl+Alt+t
$ sudo apt-get install python-tk
Thread: How to install Tkinter
The packages imported in the file are- Tkinter,ImageTk
- The ImageTk module contains support to create and modify Tkinter BitmapImage and PhotoImage objects from PIL images.
- class PIL.ImageTk.PhotoImage(image=None, size=None, **kw) -> A Tkinter-compatible photo image. This can be used everywhere Tkinter expects an image object. If the image is an RGBA image, pixels having alpha 0 are treated as transparent. The constructor takes either a PIL image, or a mode and a size. Alternatively, you can use the file or data options to initialize the photo image object.
A ComboBox combines an entry with a list of choices available to the user. This lets them either choose from a set of values you've provided (e.g. typical settings), but also put in their own value (e.g. for less common cases you don't want to include in the list).
#The necessary packages are imported from Tkinter import * import Image, ImageTk from Root import * #local package from Main import * #local package
ComboBox Class is defined class ComboBox():
def __init__(self,x,y,Boards): #constructor of the class ComboBox
#Values to the instance variables are assigned
self.Names=x
self.Dict=y
self.Boards=Boards
self.d=0
def ValueSelected(self): #callback function which is called when the button in the combobox is clicked
A temporary string is defined self.z1.get() it is used to get value of whatever is selected self.z1.get() it will contain Logitech and TempString will contain Video1 TempString=self.Dict[self.z1.get()] #value of the selection is stored in a temporary string variable 1 is covnerted to int self.d=int(TempString[5:6]) #slicing operation is done to extract the VideoDeviceNumber self.b=self.z2.get() #value of the arduino selected is stored in self.b self.window1.quit() #the combobox window is made inactive self.window1.destroy() #the combobox window is destroyed
def CreateComboBox(self):
Windows is created self.window1=Tk() #A window is created self.window1.geometry("270x100") #specify the width and height of the window self.window1.title("Select Webcam") #title of the window is declared here A tk variable is initialized it contains the different parameters of the Window tk widgets,StringVar class is imported from Tkinter, self.z1= StringVar(self.window1) #object of StringVar() class that will store the value selected from combo box z1 will contain the first element as self.names[0] self.z1.set(self.Names[0]) #the first variable is set as default variable self.w1 =OptionMenu(self.window1,self.z1,*self.Names) #an OptionMenu tk widget is created that will display elements of self.names self.w1.pack()#OptionMenu is packed inside the window created
self.z2= StringVar(self.window1) #object of StringVar() class that will store the value selected from combo box
self.z2.set(self.Boards[0]) #default value is the first element in self.Boards
self.w2 =OptionMenu(self.window1,self.z2,*self.Boards) #OptionMenu for displaying the arduino devices is created
self.w2.pack() #OptionMenu is packed
self.b1 = Button(self.window1, text="OK", command=self.ValueSelected) #A Button widget is created which will call the function self.valueselected() on clicking
self.b1.pack() #Button is packed
self.window1.mainloop() #the window which was created is started
Explanation of the above given code is as under-