with open('t.txt', 'r') as f:

   text = f.read()

cif = ''

other = ''

for char in text:

   if char.isdigit():

       cif += char

   else:

       other += char

with open('cif.txt', 'w') as f:

   f.write(cif)

with open('other.txt', 'w') as f:

   f.write(other)