Implementing a switch case statement that uses multiple arguments to validate register input in python tkinter

Hello Iam an early beginner in python and programing in general. Iam currently working on a function in my tkinter programm that validates user input before the registration. I have already managed to successfully write such a function using else if statements, however the many conditions have caused a relatively long block of else if statements. I tried to replace the else if's with switch case statements using a dictionary. But I can't figure out how to implement one in this situation because I have to use multiple arguments. Below is the working section of my code and my attemtpted switch case statement. I hope someone can help me out.

this shows the register widgets

def register_widgets_show():
    register_text1 = Label(root, text="Enter your username", font="Arial 14 bold")
    register_text1.grid(row=8, column=0)
    register_text2 = Label(root, text="\nEnter your password", font="Arial 14 bold")
    register_text2.grid(row=10, column=0)
    register_text3 = Label(root, text="\nConfirm your password", font="Arial 14 bold")
    register_text3.grid(row=12, column=0)

    register_entry_username = Entry(root, width=30, relief="sunken", bg="light grey", font="Arial 12")
    register_entry_username.grid(row=9, column=0)
    register_entry_password = Entry(root, width=30, relief="sunken", bg="light grey", font="Arial 12", show="*")
    register_entry_password.grid(row=11, column=0)
    confirm_entry_password = Entry(root, width=30, relief="sunken", bg="light grey", font="Arial 12", show="*")
    confirm_entry_password.grid(row=13, column=0)

the function that checks all conditions, it then either shows bad input or calls the register execution function the button calling it is at the bottom

def register_validation():
    username_not_valid = register_entry_username.get()

    if register_entry_password.get() != confirm_entry_password.get():
        show_bad_input("Passwords do not match.")
    elif register_entry_username.get() == "":
        show_bad_input("Name cannot be blank.")
    elif register_entry_password.get() == "":
        show_bad_input("You must set a password.")
    elif len(register_entry_password.get()) < 6:
        show_bad_input("Password must be at least 6 characters long.")
    elif username_not_valid in open("accounts_list").read():
        show_bad_input("Username already exists.")
    elif " " in register_entry_username.get():
        show_bad_input("Name cannot contain blank space.")
    elif " " in register_entry_password.get():
        show_bad_input("Password cannot contain blank space.")
    elif len(register_entry_username.get()) > 20:
        show_bad_input("Name cannot be longer than 20 characters.")
    elif register_entry_password.get() == confirm_entry_password.get(): register_execute()

def show_bad_input(error):
    bad_input = Label(root, text=error, fg="red", font="Arial 12 bold")
    bad_input.grid(row=16, column=0)
    bad_input.after(3000, lambda: bad_input.destroy())

def register_execute():

create_account_button = Button(root, text="Create account", bg="light grey",
                               font="Arial 12 bold",command=register_validation)
create_account_button.grid(row=15, column=0)    

a picture of the gui for easier visualization

my attempt to solve the problem, how do I put all three required arguments into show_bad_input_or_register_execute ?

def register_validation(error):
    username_not_valid = register_entry_username.get()
    return {
        register_entry_password.get() != confirm_entry_password.get(): "Passwords do not match.",
        register_entry_username.get() == "": "Name cannot be blank.",
        register_entry_password.get() == "": "You must set a password.",
        len(register_entry_password.get()) < 6: "Password must be at least 6 characters long.",
        username_not_valid in open("accounts_list").read(): "Username already exists.",
        " " in register_entry_username.get(): "Name cannot contain blank space.",
        " " in register_entry_password.get(): "Password cannot contain blank space.",
        len(register_entry_username.get()) > 20: "Name cannot be longer than 20 characters.",
        register_entry_password.get() == confirm_entry_password.get(): register_execute()
    }.get(error)

def show_bad_input_or_register_execute():
    bad_input = Label(root, text=register_validation(register_entry_username.get()), fg="red", font="Arial 12 bold")
    bad_input.grid(row=16, column=0)
    bad_input.after(3000, lambda: bad_input.destroy())

def register_execute():

create_account_button = Button(root, text="Create account", bg="light grey",
                               
font="Arial 12 bold",command=show_bad_input_or_register_execute)

create_account_button.grid(row=15, column=0)