On Sun, Feb 27, 2011 at 11:45 AM, Paul Symonds <paul.j.symo...@gmail.com> wrote: > Can someone give and explanation of what is happening with the following: > >>>> a,b = 0,1 # this assigns a = 0 and b = 1 > >>>> while b < 10: > > ... print b > ... a, b = b, a+b > ... > 1 > 1 > 2 > 3 > 5 > 8 > > >>>> a=0 >>>> b=1 >>>> while b < 1000: > > ... print b > ... a = b > ... b = a+b > ... > 1 > 2 > 4 > 8 > 16 > 32 > 64 > 128 > 256 > 512 > > > Why is this statement .. a, b = b, a+b
Python evaluates the entire right side of the assignment, then assigns it to the left side. So if a=1 and b=2, then a, b = b, a+b a,b = 2, 1+2 a,b = 2, 3 a = 2 b = 3 > different to ... a = b > ... b = a+b > Here, you're evaluating sequentially. a = b a = 2 b = a + b b = 2 + 2 b = 4. > > -- > http://mail.python.org/mailman/listinfo/python-list > -- http://mail.python.org/mailman/listinfo/python-list
