Tkinter: Calling function when button is pressed

Question

import tkinter as tk

def load(event):
    file = open(textField.GetValue())
    txt.SetValue(file.read())
    file.close()

def save(event):
    file = open(textField.GetValue(), 'w')
    file.write(txt.GetValue())
    file.close()


win = tk.Tk() 
win.title('Text Editor')
win.geometry('500x500') 

# create text field
textField = tk.Entry(win, width = 50)
textField.pack(fill = tk.NONE, side = tk.TOP)

# create button to open file
openBtn = tk.Button(win, text = 'Open', command = load())
openBtn.pack(expand = tk.FALSE, fill = tk.X, side = tk.TOP)

# create button to save file
saveBtn = tk.Button(win, text = 'Save', command = save())
saveBtn.pack(expand = tk.FALSE, fill = tk.X, side = tk.TOP)

I get the error that load and save are missing a position argument: event. I understand the error, but don't understand how to resolve it.

When you create the `tk.Button`s, you're _calling_ the functions because you have, for example, `command = load()` instead of `command = load` in the calling sequence to the constructor. — martineau, Jan 03 '17 at 15:46
While not an exact duplicate, your code shares the same problem as the code in this question: http://stackoverflow.com/q/5767228/7432 — Bryan Oakley, Jan 03 '17 at 15:46
@martineau I did that. Now its saying the Entry object does not have attribute GetValue. What is the purpose of having event as a parameter in a function anyway? — user7091463, Jan 05 '17 at 07:58

martineau · Answer 1 · 2020-11-26T07:47:34.873

Here's a runnable answer. In addition to changing the commmand= keyword argument so it doesn't call the function when the tk.Buttons are created, I also removed the event argument from the corresponding function definitions since tkinter doesn't pass any arguments to widget command functions (and your function don't need it, anyway).

You seem to be confusing event handlers with widget command function handlers. The former do have an event argument passed to them when they're called, but the latter typically don't (unless you do additional stuff to make it happen—it's a fairly common thing to need/want to do and is sometimes referred to as theThe extra arguments trick).

import tkinter as tk

# added only to define required global variable "txt"
class Txt(object):
    def SetValue(data): pass
    def GetValue(): pass
txt = Txt()
####

def load():
    with open(textField.get()) as file:
        txt.SetValue(file.read())

def save():
    with open(textField.get(), 'w') as file:
        file.write(txt.GetValue())

win = tk.Tk()
win.title('Text Editor')
win.geometry('500x500')

# create text field
textField = tk.Entry(win, width=50)
textField.pack(fill=tk.NONE, side=tk.TOP)

# create button to open file
openBtn = tk.Button(win, text='Open', command=load)
openBtn.pack(expand=tk.FALSE, fill=tk.X, side=tk.TOP)

# create button to save file
saveBtn = tk.Button(win, text='Save', command=save)
saveBtn.pack(expand=tk.FALSE, fill=tk.X, side=tk.TOP)

win.mainloop()

score 0 · Answer 2 · answered Jan 03 '17 at 15:43

0

Remove the 'event' arguments from both function defs and remove brackets from your commands.

answered Jan 03 '17 at 15:43

Luke.py

965
8
17

score 0 · Answer 3 · answered May 29 '18 at 14:37

Use button.bind() mehtod and pass 'Button-1' in first argument and function name in second argument def functionname(event): #your code

button = tk.Button(win, text="Login", bg="green")#, command=attempt_log_in)
button.grid(row=5, column=2)
button.bind('<Button-1>', functionname)

Tomache George Alexandru · Answer 4 · 2020-02-07T12:15:13.560

You have functions save and load that takes 1 argument : event but when you called

# create button to open file
openBtn = tk.Button(win, text = 'Open', command = **load()**) <<<--- no argument in load
                                                       <<<---should be load(someEvent)
openBtn.pack(expand = tk.FALSE, fill = tk.X, side = tk.TOP)
# create button to save file
saveBtn = tk.Button(win, text = 'Save', command = **save()**)<<< ---- same for the save
saveBtn.pack(expand = tk.FALSE, fill = tk.X, side = tk.TOP)

But in your function save and load the argument : event you don't do nothing with it so you can just delete the event argument and this problem shouldn't appear. Like this :

def load():
    file = open(textField.GetValue())
    txt.SetValue(file.read())
    file.close()

def save():
    file = open(textField.GetValue(), 'w')
    file.write(txt.GetValue())
    file.close()

Tkinter: Calling function when button is pressed

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