[Tutor] What does parent=0 mean?

[Kent Johnson]

A function or method definition can have optional arguments. These are 
function arguments that may be omitted by the caller. If they are omitted, 
they take on a default value given in the function definition. So
   def __init__(self, parent=0):
defines a function called __init__ that has one required argument (self) 
and one optional argument (parent) whose default value is 0.

In this particular case, the default argument of 0 is interpreted to mean, 
"use the root window".

This page in the Python tutorial has more information about default 
arguments: http://docs.python.org/tut/node6.html#SECTION006710000000000000000

Kent

At 08:24 PM 8/24/2004 +0200, Klas Marteleur wrote:
>Hi
>I am going thru theGUI programing chapter in Alans latest web tutorial. And
>found this example:
>
>-----------------------------------------
>from Tkinter import *
>
>class ClearApp:
>    def __init__(self, parent=0):
>       self.mainWindow = Frame(parent)
>       # Create the entry widget
>       self.entry = Entry(self.mainWindow)
>       self.entry.insert(0,"Hello world")
>       self.entry.pack(fill=X)
>
>       # now add the 2 buttons, use a grooved effect
>       fButtons = Frame(fOuter, border=2, relief="groove")
>       bClear = Button(fButtons, text="Clear",
>                       width=8, height=1, command=self.clearText)
>       bQuit = Button(fButtons, text="Quit",
>                       width=8, height=1, command=self.mainWindow.quit)
>       bClear.pack(side="left", padx=15, pady=1)
>       bQuit.pack(side="right", padx=15, pady=1)
>       fButtons.pack(fill=X)
>       self.mainWindow.pack()
>
>       # set the title
>       self.mainWindow.master.title("Clear")
>
>    def clearText(self):
>       self.entry.delete(0,END)
>
>app = ClearApp()
>app.mainWindow.mainloop()
>--------------------------------------------
>
>What does parent=0 mean?
>
>Klas
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