import re

s = open('testo.txt').read()

print("espressione 'il':")
i = re.finditer('il', s)
for m in i:
      print(m.group())

print("espressione ' il ':")
i = re.finditer(' il ', s)
for m in i:
      print(m.group())

print("espressione r'\\bil\\b':")
i = re.finditer(r'\bil\b', s)
for m in i:
      print(m.group())