Make the button enabled when text is entered in Entry widget on Tkinter

So I am trying to make the button enabled when text is entered in entry widget using tkinter however I don’t think of an idea for it to work. My code is:

def capture():
    if e.get():
        button['state'] = 'normal'

e = Entry(root, font = 20,borderwidth=5,command = capture)
e.pack()

However I do know that Entry widget has no parameter called command.

Answer

One of the ways to achieve this is using StringVar:

def capture(*args):
    if e.get():
        button['state'] = 'normal'
    else:
        button['state'] = 'disabled'

var = StringVar()
e = Entry(root, font = 20,borderwidth=5,textvariable=var)
e.pack()

var.trace('w',capture)

trace() will call the provided callback each time the value of var is changed.

The second way is to use bind:

def capture():
    if e.get():
        button['state'] = 'normal'
    else:
        button['state'] = 'disabled'

e = Entry(root, font = 20,borderwidth=5)
e.pack()
e.bind('<KeyRelease>',lambda e: capture()) # Bind keyrelease to the function

With bind, each time the key is released the function is called, whatever the key maybe. This might be a bit better because you are not creating a StringVar just for the sake of using its trace.