OOP has always driven me crazy. I read the material and follow the
examples until I feel I understand them, but when I try to implement it
I end up with an error filled mess.
So I decided to give it another try. When I got to the chapter on
tkinter I decided to solve all the exercises using OOP even though the
book solutions did not use OOP. The first one went fine:
#exer1.py
import tkinter
class Goodbye:
def __init__(self):
self.frame = tkinter.Frame(window)
self.frame.pack()
self.goodbye_button = tkinter.Button(self.frame, text='Goodbye',
#command=quit)
command=lambda: quit() )
self.goodbye_button.pack()
def quit():
self.window.destroy()
if __name__=='__main__':
window = tkinter.Tk()
myapp = Goodbye()
window.mainloop()
The second one was more trouble but I finally got it to work.
# exer2.py
import tkinter
class Count:
def __init__(self):
''' Increment a button labeled 0, by 1 with each click '''
self.frame = tkinter.Frame(window)
self.frame.pack()
self.label = tkinter.StringVar()
self.label.set('0')
self.count_btn = tkinter.Button(self.frame, textvariable=self.label,
command=lambda: self.increment(self.label ))
self.count_btn.pack()
def increment(self, label):
count = int(self.label.get())
self.label.set(str(count + 1))
if __name__ == '__main__':
window = tkinter.Tk()
myapp = Count()
window.mainloop()
I am having trouble understanding the difference between the two lines
that contain lambda: command= .In exer1.py I can do command=lambda:
quit(). In exer2.py if I do command=lambda: increment(self.label) I get
this error:
Exception in Tkinter callback
Traceback (most recent call last):
File "/usr/lib/python3.4/tkinter/__init__.py", line 1536, in __call__
return self.func(*args)
File "exer2.py", line 14, in <lambda>
command=lambda: increment(self.label ))
NameError: name 'increment' is not defined
Why do I get this error? The situations look the same to me but they
must be different somehow and I just don't see the difference.
Thanks, Jim
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