Some things to try (assuming there is no space in the last name - that is not a name like Van Gogh):
>>> name = 'Doe M Jane'
>>> ', '.join(name.split(" ", 1))
'Doe, M Jane'
>>> " ".join(name.split(" ", 1).__reversed__()).replace(',','')
'M Jane Doe'
>>> name = 'Doe, M Jane'
>>> if ',' not in name:
', '.join(name.split(" ", 1))
>>> name
'Doe, M Jane'
>>> name = 'Doe M Jane'
>>> if ',' not in name:
', '.join(name.split(" ", 1))
'Doe, M Jane'