how to get label to update based on input in entry?-CodePudding

was trying to implement a feature in a project i was doing where you enter text into an entry box and then it would times the amount of charaters in the entry by 0.02. i wanted to make it so there is a label and it would update automaticly as the user typed in the entry box but i cant seem to get it working

window = Tk()
window.geometry("600x500")
message_label = Label(window, text= "enter message").pack()
message_entry = Entry(window)
message_entry.pack()
message_length = (len(message_entry.get()))
message_price = message_length * 0.02


msg_price = Label(window)
msg_price.pack()
msg_price.config(text=message_price)

(i know this could be done easily with a button but im not trying to do this with a button)

CodePudding user response：

I would propose binding the KeyRelease event for the entry widget to a function. This, in my opinion, is simpler than using trace on a StringVar.

from tkinter import *

def updateLabel(e):
    message_length = (len(message_entry.get()))
    message_price = message_length * 0.02
    msg_price.config(text=message_price)

window = Tk()
window.geometry("600x500")
message_label = Label(window, text= "enter message")
message_label.pack()

message_entry = Entry(window)
message_entry.pack()
message_entry.bind('<KeyRelease>',updateLabel)

msg_price = Label(window)
msg_price.pack()


window.mainloop()

The updateLabel function will be updated after each key is released inside the message_entry widget

CodePudding user response：

You can add a StringVar to an Entry and then use the trace function to get updates when it has been written to using the "w" mode.

myvar = StringVar()
myEntry = Entry(master, textvariable=myvar)
myvar.trace("w", lambda a, b, c, e=Event(), v=myvar, en=entry: get_output(a, b, c, e, v, en))
myEntry.pack(side=TOP)

def get_output(a, b, c, e, v, en): #a, b and c are autogenerated name, index and mode
   #Event() might not be needed but best to include it as it can sometimes be automatically passed
    print(en.get(0, END))
    print(sv.get())

CodePudding user response：

You can use this code (entry is named "e" and label is named "l")

var = StringVar()
e = Entry(root, textvariable=var)
l = Label(root, textvariable=var)