Do you see how writing the values on two separate lines gives you the answer back on two separate lines as well? If you write everything on one line, it will print it back on one line as well, so your code should look line this:
from datetime import datetime
now = datetime.now()
print '%s/%s/%s %s:%s:%s' % ( now.month, now.day , now.year, now.hour, now.minute, now.second)
Do you understand why you had to write it like that? Let me know if you didn't or need more help.