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Why is my Button's command executed immediately when I create the Button, and not when I click it? [duplicate]
(5 answers)
Closed 2 years ago.
So i am trying to get an text input for my program but tkinter doesn't seem to register it,
and i don't know what i have done wrong
window = self.newWindow(value)
label = tk.Label(window, text="Intfix to Postfix Convert")
label.place(x=0, y=20)
e1 = tk.Entry(window)
text = e1.get()
e1.place(x=0, y=50)
rezultat = tk.Text(window, width=20, height=3)
rezultat.place(x=0, y=80)
button = tk.Button(window, text="Enter")
button.place(x=127, y=46)
button.bind("<Double-Button-1>", self.passValue(rezultat, text))
My code looks something like this. Everything else is working the self.newWindow(value) is just
a function that creates a new window from the main one
so i said text=e1.get() but i ran the debbuger and it says it is an empty string and i want to pass this text through the function passValue()(a function that passes the value to the controller), i used button.bind() to do that. Is that ok?
I tested it by putting a default value at text like text="My name" and it did pass the value so that should be in order but i don't know why doesn't it get it from the entry box like it should.
I even tried to do e1.insert(0,"some random thing") and text= e1.get() and it did get it so i think there's a problem with the input.
Do i need to use some special kind of input function?
The whole code:
class Gui:
def __init__(self, controller):
self.main = tk.Tk()
self.main.title("DSA Quiz Helper")
self.__controller = controller
def IntFixPostExecute(self, event):
widget = event.widget
selection = widget.curselection()
value = widget.get(selection[0])
self.IntfixPostfixWindow(value)
def mainWindow(self):
self.main.geometry("800x500")
# to do scrollbar
lb = tk.Listbox(self.main, width=50, height=30)
lb.insert(1, "Intfix and Postfix Calculator")
lb.insert(2, "Something else")
lb.bind("<Double-Button-1>", self.IntFixPostExecute)
lb.pack()
def IntfixPostfixWindow(self, value):
window = self.newWindow(value)
label = tk.Label(window, text="Intfix to Postfix Convert")
label.place(x=0, y=20)
e1 = tk.Entry(window)
text = e1.get()
e1.place(x=0, y=50)
rezultat = tk.Text(window, width=20, height=3)
rezultat.place(x=0, y=80)
button = tk.Button(window, text="Enter")
button.place(x=127, y=46)
button.bind("<Double-Button-1>", self.passValue(rezultat, text))
print(text)
def passValue(self, rezultat, value):
returnValue = self.__controller.InfixToPostC(rezultat, value)
rezultat.insert(tk.INSERT, returnValue)
def newWindow(self, msg):
newwind = tk.Toplevel(self.main)
q1 = tk.Frame(newwind)
q1.pack()
newwind.geometry("500x230")
return newwind
def run(self):
self.mainWindow()
self.main.mainloop()
if i set this manually it works. I don't understand why i doesn't work from entrybox input
text = tk.StringVar()
e1 = tk.Entry(window, textvariable=text)
text.set("x+y*2")
text = e1.get()
e1.place(x=0, y=50)
I think i figured it out (correct me if i am wrong). I think there is a problem
with the button because as soon as a newwindow is open, the button automatically clicks itself, when at first in the entry box there is no text written yet(so it sends to the controller with the initial text(which is empty)). The problem is why the button auto-clicks itself( or anyway auto-runs the function passValue) and why after i input the text and click the button again it does nothing(so as i understand it works only one time and auto-runs itself, at first there is no text in entrybox and the button auto-runs itself,therefore passing an empty string
You should use entryname.get() to get the text that is inside that entry instead of declaring stringVar() and making that much more unreadable and hard to comprehend and to work with. But this is my point of view! – Tiago Oliveira 48 mins ago
I think what is happening is that u use the method right after declaring the entry widget wich means u are going to get a "" empty string because that's nothing that was written there, u need to replace on the command parameter with entryname.get() instead of declaring variable = entryname.get() and passing that as parameter wich will always be empty! Hope this helps!
Related
There's an example of my code below.
I am trying to make a GUI with tkinter, in python. I want an app that has a variable, let's say var_list, that is introduced into a function as a parameter.I run this function using a button with command=lambda: analize(var_list)
I want to be able to modify the variable by pressing buttons (buttons to add strings to the list). And I have a function for that aswell:
def button_clicked(e):
if ((e["text"]).lower()) in var_list:
var_list.pop(var_list.index((e["text"]).lower())) #this adds a string to the list
else:
var_list.append((e["text"]).lower()) #this deletes the string from the list if it was already there
The function works, I tried printing the var_list and it gets updated everytime I press a button.
The problem is that I have to create the var_list as an empty list before, and when I run the function analize(var_list), it uses the empty list instead of the updated one.
Any idea on how to update the global var everytime I add/delete something from the list?
from tkinter import *
from PIL import ImageTk
def show_frame(frame):
frame.tkraise()
def button_clicked(e):
if ((e["text"]).lower()) in var_list:
var_list.pop(var_list.index((e["text"]).lower()))
else:
var_list.append((e["text"]).lower())
def analize(x):
#does stuff with the list
window = Tk()
frame1 = Frame(window)
frame2 = Frame(window)
canvas1 = Canvas(frame1,width = 1280, height = 720)
canvas1.pack(expand=YES, fill=BOTH)
image = ImageTk.PhotoImage(file="background.png")
var_list = []
button1 = Button(canvas1, text="Analize",font=("Arial"),justify=CENTER, width=10, command=lambda: [show_frame(frame2),analize(x=var_list)])
button1.place(x=(1280/2)-42, y=400)
button2 = Button(canvas1, text="String1",font=("Arial"),justify=CENTER, width=10, command=lambda: button_clicked(button2))
button2.place(x=(1280/2)-42, y=450)
button3 = Button(canvas1, text="String2",font=("Arial"),justify=CENTER, width=10, command=lambda: button_clicked(button3))
button3.place(x=(1280/2)-42, y=500)
Thank you
you can make a global variable eg:-global var
Now you can access it within other defination to manipulate the variable like this
global var
var = 0 # if you want to set a default value to the variable before calling the
function
def change_var():
global var
var = 1
USE OF GLOBAL
using global is highly recommended and is quite necessary if you are working with functions that contain or has the need to manipulate the variable
If global is not given inside the function, the variable will live inside the function and it cannot be accessed outside the function.
Hope this answer was helpful, btw, I am not sure if this the answer you are looking for as your question is not clear, maybe give a situation where you might think it might be necessary to change or update the variable
Sorry, I did not understand you but I guess this example will help you -
import tkinter as tk
root = tk.Tk()
var_list = []
def change_val(n):
var_list.append(n)
label1.config(text=var_list)
def remove():
try:
var_list.pop()
label1.config(text=var_list)
except:
pass
label1 = tk.Label(root,text=var_list)
label1.pack()
button1 = tk.Button(root,text='1',command=lambda:change_val(1))
button1.pack()
button2 = tk.Button(root,text='2',command=lambda:change_val(2))
button2.pack()
button3 = tk.Button(root,text='3',command=lambda:change_val(3))
button3.pack()
button4 = tk.Button(root,text='Pop Element',command=remove)
button4.pack()
root.mainloop()
How would I add a placeholder to an entry in tkinter? I don't believe it has a placeholder function like HTML for example. I figured out that to make the text disappear when you click it, you will have to add an onclick event, but how do I create the onclick event and how do you make the text appear in the first place? Here is the code I'm working with.
I would like it to say " Enter your integer here"
Textbox
vcmd = (self.register(self.onValidate), '%S')
self.text = Entry(self, validate='key', vcmd=vcmd)
self.text.pack()
def onValidate(self, S):
if S in '0123456789.':
return True
return False
def clear_entry(self):
self.text.delete(0, END)
self.text.pack()
U can't add placeholder like HTML as far as i know, but u can make similar behavior. When you make entry you can do something like>
from tkinter import *
def clear_entry(event, entry):
entry.delete(0, END)
root = Tk()
entry = Entry(root)
entry.pack()
placeholder_text = 'some text'
entry.insert(0, placeholder_text)
entry.bind("<Button-1>", lambda event: clear_entry(event, entry))
root.mainloop()
P.S: I've wrote this from my head , haven't tested it
In the program I made, the user presses enter and the text typed is then shown as a label in the program. So the label keeps getting updated and then written on the next line. The problem is that in the textbox the previous line the user typed stays there, which means u have to keep manually deleting the string in the textbox to write a new line. How can I make it so that you start out with a cleared textbox? Also, the enter button works but it seems that when i click on the "Return" button it gives me an error:
TypeError: evaluate() missing 1 required positional argument: 'event'
Here's the code:
from tkinter import *
window = Tk()
window.geometry("200x300")
def evaluate(event):
thetext = StringVar()
labeloutput = Label(app, textvariable = thetext)
n = e.get()
thetext.set(n)
labeloutput.grid()
app = Frame(window)
app.pack()
e = Entry(window)
e.pack()
b= Button(window, text="Return", command=evaluate)
b.pack()
window.bind("<Return>", evaluate)
mainloop()
Since you bind evaluate as a callback and you use it as a button command, when you use it in the button you have to use a lambda and pass None to the event. event argument is needed because of the binding, but there is no event when you call it from button click, so just pass None to get rid of the error. You can delete by doing entry.delete(0, 'end').
from tkinter import *
window = Tk()
window.geometry("200x300")
def evaluate(event):
thetext = StringVar()
labeloutput = Label(app, textvariable = thetext)
n = e.get()
thetext.set(n)
labeloutput.grid()
e.delete(0, 'end') # Here we remove text inside the entry
app = Frame(window)
app.pack()
e = Entry(window)
e.pack()
b = Button(window, text="Return", command=lambda: evaluate(None)) # Here we have a lambda to pass None to the event
b.pack()
window.bind("<Return>", evaluate)
mainloop()
Of course, if you want to prevent the lambda from being used, you would have to create a function to handle the key binding, and a separate one for the button click.
I'm trying to use an Entry field to get manual input, and then work with that data.
All sources I've found claim I should use the get() function, but I haven't found a simple working mini example yet, and I can't get it to work.
I hope someone can tel me what I'm doing wrong. Here's a mini file:
from tkinter import *
master = Tk()
Label(master, text="Input: ").grid(row=0, sticky=W)
entry = Entry(master)
entry.grid(row=0, column=1)
content = entry.get()
print(content) # does not work
mainloop()
This gives me an Entry field I can type in, but I can't do anything with the data once it's typed in.
I suspect my code doesn't work because initially, entry is empty. But then how do I access input data once it has been typed in?
It looks like you may be confused as to when commands are run. In your example, you are calling the get method before the GUI has a chance to be displayed on the screen (which happens after you call mainloop.
Try adding a button that calls the get method. This is much easier if you write your application as a class. For example:
import tkinter as tk
class SampleApp(tk.Tk):
def __init__(self):
tk.Tk.__init__(self)
self.entry = tk.Entry(self)
self.button = tk.Button(self, text="Get", command=self.on_button)
self.button.pack()
self.entry.pack()
def on_button(self):
print(self.entry.get())
app = SampleApp()
app.mainloop()
Run the program, type into the entry widget, then click on the button.
You could also use a StringVar variable, even if it's not strictly necessary:
v = StringVar()
e = Entry(master, textvariable=v)
e.pack()
v.set("a default value")
s = v.get()
For more information, see this page on effbot.org.
A simple example without classes:
from tkinter import *
master = Tk()
# Create this method before you create the entry
def return_entry(en):
"""Gets and prints the content of the entry"""
content = entry.get()
print(content)
Label(master, text="Input: ").grid(row=0, sticky=W)
entry = Entry(master)
entry.grid(row=0, column=1)
# Connect the entry with the return button
entry.bind('<Return>', return_entry)
mainloop()
*
master = Tk()
entryb1 = StringVar
Label(master, text="Input: ").grid(row=0, sticky=W)
Entry(master, textvariable=entryb1).grid(row=1, column=1)
b1 = Button(master, text="continue", command=print_content)
b1.grid(row=2, column=1)
def print_content():
global entryb1
content = entryb1.get()
print(content)
master.mainloop()
What you did wrong was not put it inside a Define function then you hadn't used the .get function with the textvariable you had set.
you need to put a textvariable in it, so you can use set() and get() method :
var=StringVar()
x= Entry (root,textvariable=var)
Most of the answers I found only showed how to do it with tkinter as tk. This was a problem for me as my program was 300 lines long with tons of other labels and buttons, and I would have had to change a lot of it.
Here's a way to do it without importing tkinter as tk or using StringVars. I modified the original mini program by:
making it a class
adding a button and an extra method.
This program opens up a tkinter window with an entry box and an "Enter" button. Clicking the Enter button prints whatever is in the entry box.
from tkinter import *
class mini():
def __init__(self):
master = Tk()
Label(master, text="Input: ").grid(row=0, sticky=W)
Button(master, text='Enter', command=self.get_content).grid(row=1)
self.entry = Entry(master)
self.entry.grid(row=0, column=1)
master.mainloop()
def get_content(self):
content = self.entry.get()
print(content)
m = mini()
I'm trying to use an Entry field to get manual input, and then work with that data.
All sources I've found claim I should use the get() function, but I haven't found a simple working mini example yet, and I can't get it to work.
I hope someone can tel me what I'm doing wrong. Here's a mini file:
from tkinter import *
master = Tk()
Label(master, text="Input: ").grid(row=0, sticky=W)
entry = Entry(master)
entry.grid(row=0, column=1)
content = entry.get()
print(content) # does not work
mainloop()
This gives me an Entry field I can type in, but I can't do anything with the data once it's typed in.
I suspect my code doesn't work because initially, entry is empty. But then how do I access input data once it has been typed in?
It looks like you may be confused as to when commands are run. In your example, you are calling the get method before the GUI has a chance to be displayed on the screen (which happens after you call mainloop.
Try adding a button that calls the get method. This is much easier if you write your application as a class. For example:
import tkinter as tk
class SampleApp(tk.Tk):
def __init__(self):
tk.Tk.__init__(self)
self.entry = tk.Entry(self)
self.button = tk.Button(self, text="Get", command=self.on_button)
self.button.pack()
self.entry.pack()
def on_button(self):
print(self.entry.get())
app = SampleApp()
app.mainloop()
Run the program, type into the entry widget, then click on the button.
You could also use a StringVar variable, even if it's not strictly necessary:
v = StringVar()
e = Entry(master, textvariable=v)
e.pack()
v.set("a default value")
s = v.get()
For more information, see this page on effbot.org.
A simple example without classes:
from tkinter import *
master = Tk()
# Create this method before you create the entry
def return_entry(en):
"""Gets and prints the content of the entry"""
content = entry.get()
print(content)
Label(master, text="Input: ").grid(row=0, sticky=W)
entry = Entry(master)
entry.grid(row=0, column=1)
# Connect the entry with the return button
entry.bind('<Return>', return_entry)
mainloop()
*
master = Tk()
entryb1 = StringVar
Label(master, text="Input: ").grid(row=0, sticky=W)
Entry(master, textvariable=entryb1).grid(row=1, column=1)
b1 = Button(master, text="continue", command=print_content)
b1.grid(row=2, column=1)
def print_content():
global entryb1
content = entryb1.get()
print(content)
master.mainloop()
What you did wrong was not put it inside a Define function then you hadn't used the .get function with the textvariable you had set.
you need to put a textvariable in it, so you can use set() and get() method :
var=StringVar()
x= Entry (root,textvariable=var)
Most of the answers I found only showed how to do it with tkinter as tk. This was a problem for me as my program was 300 lines long with tons of other labels and buttons, and I would have had to change a lot of it.
Here's a way to do it without importing tkinter as tk or using StringVars. I modified the original mini program by:
making it a class
adding a button and an extra method.
This program opens up a tkinter window with an entry box and an "Enter" button. Clicking the Enter button prints whatever is in the entry box.
from tkinter import *
class mini():
def __init__(self):
master = Tk()
Label(master, text="Input: ").grid(row=0, sticky=W)
Button(master, text='Enter', command=self.get_content).grid(row=1)
self.entry = Entry(master)
self.entry.grid(row=0, column=1)
master.mainloop()
def get_content(self):
content = self.entry.get()
print(content)
m = mini()