Newbie question, problem with functions

[Rickard Karlsson]

I have wrote this little program, that is supposed to execute eg. the
Linux ls command when you press a button. Te problem is that all the
commands are run automaticly and they won't run when I press the
associated button. Wath am I do wrong?

from Tkinter import *
import os

class App:

def __init__(self, master):

frame = Frame(master)
frame.pack()

b1 = Button(frame, text = "ls", command = self.execute('ls'))
b2 = Button(frame, text = "ls -alh", command = self.execute('ls
-alh'))
b3 = Button(frame, text = "pwd", command = self.execute('pwd'))

b1.grid(column=0, row=1)
b2.grid(column=0, row=2)
b3.grid(column=0, row=3)

def execute(self,com):
os.system(com)

root = Tk()

app = App(root)

root.mainloop()

 

[Peter Otten]

I have wrote this little program, that is supposed to execute eg. the
Linux ls command when you press a button. Te problem is that all the
commands are run automaticly and they won't run when I press the
associated button. Wath am I do wrong?
[...]
b1 = Button(frame, text = "ls", command = self.execute('ls'))
b2 = Button(frame, text = "ls -alh", command = self.execute('ls
-alh'))
b3 = Button(frame, text = "pwd", command = self.execute('pwd'))

[...]

You are in fact passing the result of self.execute(...), i. e. None, instead
of the method. Do

b3 = Button(frame, text="pwd", command=lambda: self.execute('pwd'))

instead or define wrapper methods like so:

def executeLs(self):
self.execute("ls")

and assign them to the buttons without a trailing (), e. g.:

b1 = Button(frame, text="ls", command=self.executeLs)

Peter

 

[Rickard Karlsson]

You are in fact passing the result of self.execute(...), i. e. None, instead

of the method. Do

b3 = Button(frame, text="pwd", command=lambda: self.execute('pwd'))

Thank you so much, it works fine now.