s = "Hello Python!"

# convert all characters to lowercase
print(s.lower())
# output : hello python!

# convert all characters to uppercase
print(s.upper())
# output : HELLO PYTHON!

# check if string starts with 'He'
print(s.startswith('He'))
# output : True

# check if string ends with '?'
print(s.endswith('?'))
# output : False

# replace a portion of string
s2 = s.replace('Python', 'C++')
print(s2)
# output : Hello C++!