import re
mh="mahmud hossain a good boy "
x=re.sub("s","5",mh)
print(x)

import re
mh="mahmud hossain a good boy "
x=re.sub("\s","5",mh)
print(x)

import re
mh="mahmud hossain a good boy "
x=re.sub("\s","5",mh,2)
print(x)

