python - Why is Tkinter Entry's get function returning nothing?

Question

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?

Answer 1

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.