main.py

def stud_lgn_btn(window):
    # Killing the previous window and moving to the student window
    window.destroy()

    # Making the tkinter window global
    global root

    # Creating new window
    root = Tk()

    root.title("STUDENT LOGIN")
    root.geometry("960x600")
    root.resizable(0, 0)
    root.iconbitmap("./ico/student.ico")

    # Creating String Vars
    global username_var
    global passw_var
    username_var = StringVar()
    passw_var = StringVar()

    # Creating the background image variable
    bg = PhotoImage(file="./img/all_lgn.png")

    # Creating the label background
    l1 = Label(root, image=bg)
    l1.place(x=0, y=0)

    # Creating student login text
    l2 = Label(root, text="STUDENT LOGIN", background="#413E91",
               font=("times new roman", 20, "bold"), fg="black")
    l2.place(x=385, y=13)

    # Creating the login username text
    lgnt1 = Label(root, text="USERNAME", font=("times new roman", 10, "bold"))
    lgnt1.place(x=40, y=140)

    # Creating the username login entry form
    global user
    user = Entry(root, textvariable=username_var, width=20)
    user.place(x=140, y=140)

    # Creating the login password text
    lgnt2 = Label(root, text="PASSWORD", font=("times new roman", 10, "bold"))
    lgnt2.place(x=40, y=180)

    # Creating the password entry form
    pswd = Entry(root, textvariable=passw_var, width=20, show="*")
    pswd.place(x=140, y=180)

    # Creating the submit button
    submit = Button(root, text="SUBMIT", command=stud_lgn)
    submit.place(x=130, y=220)

    root.mainloop()

"""
The stud_lgn() function is used to check for the username and password in the database and make further movements
Tt uses the global username_var and password_var for checking the values
It used .get() method to get the str() return of the entered value from the report
Then that value is used to validate the student using mysql connection

If the entered value is correct then this window proceeds into stud_home()
If not then the window will show an error message stating 'Cannot find such a user with the given username and passweord. Please retry'
"""
def stud_lgn():
    name = username_var.get()
    passw = passw_var.get()

    cur.execute(
        "SELECT * FROM STUDENTS WHERE USERNAME=%s AND PASSWORD=%s", (name, passw))

    a = cur.fetchone()

    global L
    L = []

    if a !=None and len(a) != 0:
        for k in a:
            L.append(k)

        root.destroy()
        stud_home()

    else:
        messagebox.showerror(
            "User nor found", "Cannot find such a user with the given username and password. Please retry")

    username_var.set("")
    passw_var.set("")