How can I disable a button after pressed?

Question

I want to disable a Tkinter button after I pressed it.

This is my effort so far:

class Pag4(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        label = tk.Label(self, text="Alege prelucrarea")
        label.pack(pady=10,padx=10)
        self.controller = controller
        label = tk.Label(self, text="Pagina 4")
        button = tk.Button(self, text="Srunjire", command=lambda: controller.show_frame("Pag20"))
      
        button.pack()

Answer 1

You need 1) to track your button (so store it as class variable) and 2) to change button state via its state property.

Assuming you attach manage_button function to the button, your code becomes this:

def enable_button(button:tk.Button):
    button["state"] = "normal"

def disable_button(button:tk.Button):
    button["state"] = "disabled"

class Pag4(tk.Frame):
    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        label = tk.Label(self, text="Alege prelucrarea")
        label.pack(pady=10,padx=10)
        self.controller = controller
        label = tk.Label(self, text="Pagina 4")
        self.button = tk.Button(self, text="Srunjire", command=lambda: controller.show_frame("Pag20"))
      
        self.button.pack()

    def manage_button():
        if self.button.cget("state") == "normal":
            disable_button(self.button)
        else:
            enable_button(self.button)

Answer 2

You can use .config(state="disabled") to disable the button. Better create a new function for the command option of the button and then disable the button and call controller.show_frame(...) inside that new function:

class Pag4(tk.Frame):

    def __init__(self, parent, controller):
        tk.Frame.__init__(self, parent)
        label = tk.Label(self, text="Alege prelucrarea")
        label.pack(pady=10,padx=10)
        self.controller = controller
        label = tk.Label(self, text="Pagina 4") # note that this label is not visible
        self.button = tk.Button(self, text="Srunjire", command=self.on_button_clicked)
        self.button.pack()

    def on_button_clicked(self):
        self.button.config(state="disabled")
        self.controller.show_frame("Pag20")

Note that button is changed to instance variable self.button so that it can be accessed inside the new function.