Typing string.whitespace gives you a string containing all whitespace characters defined by Python\'s string module:
\'\\t\\n\\x0b\\x0c
\v is \x0b:
>>> '\v'
'\x0b'
but the string literal representation in Python is using the \x0b notation instead.
The Python string literal representation only ever uses \n, \r and \t, everything else that is not a printable ASCII character is represented using the \xhh notation instead.
\x0c is a form feed; it forces a printer to move to the next sheet of paper. You can also express it as \f in Python:
>>> '\f'
'\x0c'
In terminals the effects of \v and \f are often the same.