'Hello world'.upper()
#HELLO WORLD
'Hello world'.lower()
#hello world
'Hello world'.title()
#Hello World
'Hello world'.split()
#['Hello', 'world']

' '.join(['Hello', 'world'])
#'Hello world'
'Hello world'.replace('H', 'J')
#'Jello world'
'   Hello world   '.strip()
#'Hello world'
"{} {}".format("Hello", "world")
#'Helloo world'

'Hello world'.upper()
#HELLO WORLD
'Hello world'.lower()
#hello world
'Hello world'.title()
#Hello World
'Hello world'.split()
#['Hello', 'world']

' '.join(['Hello', 'world'])
#'Hello world'
'Hello world'.replace('H', 'J')
#'Jello world'
'   Hello world   '.strip()
#'Hello world'
"{} {}".format("Hello", "world")
#'Helloo world'

#HELLO WORLD #hello world #Hello World #['Hello', 'world'] #'Hello world' #'Jello world' #'Hello world' #'Helloo world'