# strings are immutable in Python,
# we have to create a new string which
# includes the value at the desired index
s = s[:index] + newstring + s[index + 1:]mystring = 'hello, world'
mylist = string1.split(', ') #output => ['hello', 'world']
myjoin1 = ', '.join(mylist) #output => 'hello, world'
myjoin2 = ' '.join(mylist) #output => 'hello world'
myjoin3 = ','.join(mylist) #output => 'hello,world'sentence = 'Python programming is fun.'
result = sentence.index('is fun')
print("Substring 'is fun':", result)
result = sentence.index('Java')
print("Substring 'Java':", result)