Ошибка PySerial

from tkinter import*
import serial
import serial.tools.list_ports
win = Tk()
win.title("ПРОК - Пальцы Работают Отличной Клавиатурой")
x=160
ss = ""
al = ["a", "b", "c", "d", "e", 'f', "g"]
width = win.winfo_screenwidth()
height = win.winfo_screenheight()
win.geometry("%dx%d" % (width, height))
win.state('zoomed')
def main():
    while True:
        n =ser.readline()
        if n != "":
            i = dec(n)
            try:
                s = al[i]
            except:
                s = ""
            try:
                fi= open(e2.get(),"r")
                fi= open(e2.get,"a")
            except:
                fi = open(e2.get(), "w")
            fi.write(s)
            fi.close()
 
            text.insert(2.2, s)
            win.update()
def dec(st):
    n = str(st).replace("\\", "").replace("b'", "").replace("'", "").replace("r", "").replace("n", "").replace("x", "")
    return int(n, base = 16)
ports = list(serial.tools.list_ports.comports())
for p in ports:
    if "CH340" in p.description:
        port = p.device
ser = serial.Serial(port, 9600, timeout=2)
j = 0
canv = Canvas(win, bg = "lightblue")
canv.pack(fill = "both", expand = True)
def impu(u):
    imp()
def imp():
    global e1, b1
    try:
        imp = int(e1.get())
        b1["text"] = "Сохранить длину импульса"
    except:
        b1["text"] = "Попробуйте ещё!"
text = Text(width=width-1215, height=37)
text.place(x = 80, y = 130)
scroll = Scrollbar(command=text.yview)
scroll.place(x = 80, y = 130)
b1 = Button(text = "Сохранить длину импульса", command = imp, width = 22)
e2= Entry(width = 130, bg="lightgrey")
e2.place(x=width/2-400, y = 140)
b2 = Button(text = "Начать!", command = main, width = 22)
e1 = Entry(width = 30)
e1.place(x=width/2-100, y = 40)
b1.place(x=width/2-85, y = 70)
e1.bind("<Return>", impu)
b2.place(x = width/2-75, y = 180)
canv.create_rectangle(80, 130, width-80, height+10, fill='white', outline='black',width=0.5)
win.mainloop()