Error in code NameError: name ' ' is not defined

[ppman00]

I used this code below. It program works till the line with numb.x.
In 1st stage program asking for file name. (it will save the result there)
In the next stage program asks how many digits your going to input, and that and modulo 4 from that number must be equal 0.
Third stage is input digits. Till that moment it works.
After that i receive error

from typing import List, Any, TextIO
 
  
lista: List[int] = []
 
file = str(input("file name: ")+'.txt')
 
n = int(input("give how many digits u want to input, modulo 4 must be 0: \n", ))
 
while n % 4 != 0:
    n = int(input("wrong", ))
print("give " + str(n) + " digit")
 
while len(lista) < n:
 
    digit= int(input("give digit: "))
 
    if not 0 <= digit <= 9:
        print('wrong')
    else:
        lista.append(digit)
 
print(lista)
 
m = int(len(lista)/4)
 
#print(m)
numb = 0
for i in range(0, m):
 
    x = i
    y = i + 1
 
    numb.x=int(str(lista[0 + i*4]) + str(lista[2 + i*4]))
    numb.y=int(str(lista[1 + i * 4]) + str(lista[3 + i * 4]))
 
    numb.i= (numb.x) + (numb.y)
 
    chr(numb.i)
    print(chr(numb.i), end=" ")
 
file: TextIO = open((file), 'w')
file.write(chr(numb.i))
file.close()