Python Rearranging elements in Python

[Steve389]

I am confused on lines 9-11, how does elem2 change values, surely it would just say as one since it's just swapping values with it's self? It's confusing because in order for this sequence to work it needs to change, I just don't know how it is doing so.

[CODE lang="python" highlight="9-11"]def fib(n):
if n < 1:
return None
if n < 3:
return 1

elem1 = elem2 = 1
sum = 0
for i in range(3, n + 1):
sum = elem1 + elem2
elem1, elem2 = elem2, sum
return sum

for n in range(1, 5): # testing
print(n, "->", fib(n))

[/CODE]

 

[LTomy]

Hi Steve389,

Is'nt the following:

elem1, elem2 = elem2, sum

Equivalent to?:

elem1 = elem2
elem2 = sum

'elem1' takes the old value of 'elem2' and elem2 is assigned with the current total (summation).