Hello. Could you please explain me the difference..

Question

def fibonacci(n):#
x = 0
y = 1
s = []
for i in " " * n:
s += [x]; x, y = y, x + y
return s

def fibonacci_(n):#
x = 0
y = 1
s = []
for i in " " * n:
s += [x]
x = y
y = x + y
return s

print(*fibonacci(10)) #0,1,1,2,3,5,8,13,21,34.
print(*fibonacci_(10)) #0 1 2 4 8 16 32 64 128 256

Why doesn't the "fibonacci_" function return the same as the "fibonacci" function?

Answer 1

In fibonacci_() the value of x is changed prior to being added to y and then assigned back as the value of y.
fibonacci() the current values are substituted in-line before being assigned.

Example:
x = 2
y = 3
x, y = y, x + y
This would translate to;
x, y = 3, 2 + 3
So that x would now have the value of 3, while y would now have the value of 5.
While;
x = y
y = x + y
Would translate to;
x = 3
y = 3 + 3
Here, x would get the value 3 and y would evaluate to 6.