How do I get a variable from a text input in tkinter?

Question

I have tried to get a variable from a text input by doing this:

username_var = StringVar()
user_name_input_area = Entry(top, width = 30, textvariable=username_var).place(x = 110, y = 100)
username = username_var.get()

However when I try to acess the variable in a function it does not do anything.

My two functions are:

def ifSubmit():
    writeToFile(service)
    writeToFile(username)

def writeToFile(input_variable):
    with open("password&usernames.txt", "a") as input:
        input.writelines(input_variable)

But when I open the text file, nothing appears. I have also tested with:

writeToFile('hello')

In this case I do get hello in my text file and so I suspect that it is the variables that is the probelm not the writeToFile() function.

So am I retrieving the text being inputed correctly?

Full code:

import string
import random
from tkinter import * 

mypasslist = []

with open("password&usernames.txt", "r") as input:
    for line in input:
        items = line.split()
        mypasslist.append([item for item in items[0:]])


def generatePassword():
    characters = string.ascii_letters + string.punctuation  + string.digits
    password =  "".join(random.choice(characters) for x in range(random.randint(8, 16)))
    return password

def writeToFile(input_variable):
    with open("password&usernames.txt", "a") as input:
        input.writelines(input_variable)

top = Tk()    
top.geometry("1920x1080")   

def ifSubmit():
    global a
    a = generatePassword()
    label1 = Label(top, text='Your password is: %s' % a, font=("Arial", 11)).place(x = 40, y = 170)
    label1 = Label(top, justify='left', text='Your password and username has been saved, you can access them below.').place(x = 40, y = 227)
    copy_button = Button(top, text = 'Copy', command=copyText).place(x=40, y=195)
    
    writeToFile(service)
    writeToFile(username)
    writeToFile(str(a))

def copyText():
    top.clipboard_clear()
    top.clipboard_append(a)
    top.update()

# the label for user_name  
Service = Label(top, text = "Service").place(x = 40, y = 60)   
user_name = Label(top, text = "Username").place(x = 40, y = 100)   

submit_button = Button(top, text = "Submit", command=ifSubmit).place(x = 40, y = 130) 

service_var = StringVar()
Service_input_area = Entry(top, width = 30, textvariable=service_var)
Service_input_area.place(x = 110, y = 60)
service = service_var.get()

username_var = StringVar()
user_name_input_area = Entry(top, width = 30, textvariable=username_var)
username = username_var.get()
user_name_input_area.place(x = 110, y = 100)

top.mainloop() 

Answer 1

A few things stick out:

Let's say you're creating a label widget:

label = Label(top, text="This is a label").place(x=40, y=40)

This is incorrect. label will be bound to whatever the place method returned, because you're chaining the Label instantiation and the place method. The place method always returns None , so label will be None . You need to split this up into two separate statements - one to instantiate and bind the widget, the other to place it:

label = Label(top, text="This is a label")
label.place(x=40, y=40)

You need to do this for every widget in your script, regardless of whether it's a label, button, etc.

Also, in a few places, you do something like this:

var = StringVar()
entry = Entry(..., textvariable=var)
user_input = var.get()

Which is also incorrect. You create an entry widget, and then immediately read from it using var.get . Since you just created the widget, its contents will be empty, so in this case user_input will be empty. You also never change user_input , or read from the entry widget again at a later point, so what you end up writing to the file will just be an empty string. You need to call var.get once the user has actually had a chance to write something. A button callback would be a good place to do this.

Answer 2

This answer has already has pointed out most of the mistakes.

I also see a few more things that you are doing wrong specifically under isSubmit() function. Here you are creating 2 labels and a button that would be created whenever the submit button is pressed. you either need to destroy the previous label and buttons or create a label and button only once and use place() and place_forget() to show and hide them. Also, try to avoid using python inbuilt class and function names to name your variables.

Here is your corrected code:

import string
import random
from tkinter import * 

mypasslist = []

with open(r"file.txt", "r") as inp:
    for line in inp:
        items = line.split()
        mypasslist.append([item for item in items[0:]])


def generatePassword():
    characters = string.ascii_letters + string.punctuation  + string.digits
    password =  "".join(random.choice(characters) for x in range(random.randint(8, 16)))
    return password

def writeToFile(input_variable):
    with open(r"file.txt", "a") as inp:
        inp.writelines(input_variable)

top = Tk()    
top.geometry("1920x1080")   

def ifSubmit():

    passwd = generatePassword()
    label1.config(text='Your password is: %s' % passwd)
    label1.place(x = 40, y = 170)

    label2.config(text='Your password and username has been saved, you can access them below.')
    label2.place(x = 40, y = 227)


    copy_button = Button(top, text = 'Copy', command=copyText).place(x=40, y=195)
    
    writeToFile(service_var.get()+', ')
    writeToFile(username_var.get()+', ')
    writeToFile(passwd+'\n')

def copyText():
    top.clipboard_clear()
    top.clipboard_append(passwd)
    top.update()

# the label for user_name  
Label(top, text = "Service").place(x = 40, y = 60)   
Label(top, text = "Username").place(x = 40, y = 100)   

submit_button = Button(top, text = "Submit", command=ifSubmit).place(x = 40, y = 130) 

service_var = StringVar()
Service_input_area = Entry(top, width = 30, textvariable=service_var)
Service_input_area.place(x = 110, y = 60)

username_var = StringVar()
user_name_input_area = Entry(top, width = 30, textvariable=username_var)
user_name_input_area.place(x = 110, y = 100)


# label 1
label1 = Label(top, font=("Arial", 11))
label2 = Label(top, justify='left')

copy_button = Button(top, text = 'Copy', command=copyText)


top.mainloop()