import os

first_marker = '# Vlan'
second_marker = '# '
with open(r"C:\123\des.cfg", "r") as source:
  n = 0
  for line in source:
    n += 1
    if first_marker in line:
      n_first_m = n - 1
source.close()


source_2 = ''
for linenum,line in enumerate(open(r"C:\123\des.cfg", "r")):
    if linenum>n_first_m:
        split_source = line.strip()
        source_2 = source_2 + split_source + "\n"


with open(r"C:\123\buff.cfg", "w") as f2:
    f2.write(source_2)
f2.close()

with open(r"C:\123\buff.cfg", "r") as source:
  nn = 0
  for line in source:
    nn += 1
    if second_marker in line:
        n_second_m = nn - 2
        break
source.close()

source_3 = ''
for linenum,line in enumerate(open(r"C:\123\buff.cfg", "r")):
    if linenum<n_second_m:
        split_source = line.strip()
        source_3 = source_3 + split_source + "\n"


with open(r"C:\123\source.cfg", "w") as f3:
    f3.write(source_3)
f3.close()

os.remove(r"C:\123\buff.cfg")