To swap numbers without using temporary variable

__author__ = 'nitin'

def swap_number():
    alist=[12,14,17,20,24,27]
    print "First number : ", alist[1]
    print "Second number : ", alist[2]
    alist[1]=alist[1]+alist[2]
    alist[2]=alist[1]-alist[2]
    alist[1]=alist[1]-alist[2]
    print "\nAfter Swapping \n"
    print "First number : ", alist[1]
    print "Second number : ", alist[2]

If __name=="__main":
    swap_number()