def login_check(login, lines):
for item in lines:
        if (search_user.get() == item[0] and search_pass.get() == item[1]):
            login.destroy()
            experiment_list()
        else:
            inv_login = Label(login, bg="#eee8dc")
            inv_login.grid(row=9,column=2,pady=5, columnspan=2)
            inv_login.configure(text="Invalid login.", fg="#ff0000")
def login_main(lines):
    login = Frame(main, bg="#eee8dc", height=600, width=600)
    login.grid()
    title = Label(login, text="Login.", font=Med_font, bg="#eee8dc")
    title.grid(row=2,column=1,columnspan=2,pady=10)
    #--------------------------------
    username = Label(login, text="Username.", bg="#eee8dc")
    username.grid(row=4,column=1)
    entry_user = Entry(login, textvariable=search_user)
    entry_user.grid(row=4,column=2,padx=10)
    #--------------------------------
    password = Label(login, text="Password.", bg="#eee8dc")
    password.grid(row=6,column=1)
    entry_pass = Entry(login, textvariable=search_pass)
    entry_pass.grid(row=6,column=2,padx=10)
    #--------------------------------
    submit = Button(login, text="Submit.", bg="#ffffff", command=lambda: login_check(login, lines))
    submit.grid(row=8,column=1,columnspan=2,pady=15)