How to handle a Button click event

Question

I'm just learning Python and I have the base concept down, and already a few command line programs. I'm now learning how to create GUIs with Tkinter.

I created a simple GUI to accept some user information from a Entry widget, and then, when the user clicks submit, it should pop up a dialog.

The dialog should ask for the first name and last name.

The problem is that I don't know how to handle the event when the user clicks submit.

Here's my code:

from Tkinter import *

class GUI(Frame):

    def __init__(self,master=None):
        Frame.__init__(self, master)
        self.grid()

        self.fnameLabel = Label(master, text="First Name")
        self.fnameLabel.grid()

        self.fnameEntry = Entry(master)
        self.fnameEntry.grid()

        self.lnameLabel = Label(master, text="Last Name")
        self.lnameLabel.grid()

        self.lnameEntry = Entry(master)
        self.lnameEntry.grid()

        self.submitButton = Button(self.buttonClick, text="Submit")
        self.submitButton.grid()


    def buttonClick(self, event):
        """ handle button click event and output text from entry area"""
        pass


if __name__ == "__main__":
    guiFrame = GUI()
    guiFrame.mainloop()

Solution 1

You already had your event function. Just correct your code to:

   """Create Submit Button"""
    self.submitButton = Button(master, command=self.buttonClick, text="Submit")
    self.submitButton.grid()

def buttonClick(self):
    """ handle button click event and output text from entry area"""
    print('hello')    # do here whatever you want

This is the same as in @Freak's answer except for the buttonClick() method is now outside the class __init__ method. The advantage is that in this way you can call the action programmatically. This is the conventional way in OOP-coded GUI's.

Solution 2

I found a pretty good reference called Thinking in Tkinter, and I butchered it up a bit. I tried to fit it for what you wanted.

from tkinter import *

class GUI(Frame):

    def __init__(self,master=None):
        Frame.__init__(self, master)
        self.grid()

        self.fnameLabel = Label(master, text="First Name")
        self.fnameLabel.grid()

        self.fnameEntry = StringVar()
        self.fnameEntry = Entry(textvariable=self.fnameEntry)
        self.fnameEntry.grid()

        self.lnameLabel = Label(master, text="Last Name")
        self.lnameLabel.grid()

        self.lnameEntry = StringVar()
        self.lnameEntry = Entry(textvariable=self.lnameEntry)
        self.lnameEntry.grid()

        def buttonClick():
            print("You pressed Submit!")
            print(self.fnameEntry.get() + " " + self.lnameEntry.get() +",
                  you clicked the button!")

        self.submitButton = Button(master, text="Submit", command=buttonClick)
        self.submitButton.grid()

if __name__ == "__main__":
    guiFrame = GUI()    
    guiFrame.mainloop()

Solution 3

You should specify a handler, or a function, that is called when you click the Button. You can do this my assigning the name (not calling the function) of the function to the property command of your Button.

For example:

self.submitButton = Button(self.buttonClick, text="Submit", command=buttonClick)

Note the absence of () when assigning buttonClick as the command property of self.submitButton.

Note that you don't need the second parameter called event in your handler/function buttonClick().

Comments

[dmb]

Thanks for this. I forgot that you can use function names without calling them with the ending "( )". I was wondering why the process I intended to call from a button kept popping at the same time as the GUI and this was it. I'm pretty new to GUIs