import re

# sub 
result = re.sub(r'India', 'the World', 'AV is largest Analytics community of India')
print (result)

# compile
pattern = re.compile('AV')
result = pattern.findall('AV Analytics Vidhya AV')
print (result)
result2 = pattern.findall('AV is largest analytics community of India')
print (result2)

# search
patterns = [ 'this', 'that', 'h th' ]
text = 'Does this text match the pattern?'

for pattern in patterns:
    print  ('Looking for "%s" in "%s" ->' % (pattern, text), )

    if re.search(pattern,  text):
        print ( 'found a match!' )
    else:
        print  ( 'no match' )