Difference between writing something on one line and on several lines

Question

Where is the difference when I write something on one line, seperated by a , and on two lines. Apparently I do not understand the difference, because I though t

Answer 1

To find a replacement for

a, b = b, a + b

you must become aware that this assignment is performed "step by step".

So its equivalent is

old_a = a
a = b
b = old_a + b # note the old_a here, as a has been replaced in the meanwhile.

Demo:

def fibi(n):
    a, b = 0, 1
    for i in range(n):
        a, b = b, a + b
    return a

def fibi2(n):
   a, b = 0, 1
   for i in range(n):
    old_a = a
    a = b
    b = old_a + b
   return a

>>> fibi(0)
0
>>> fibi(1)
1
>>> fibi(2)
1
>>> fibi(3)
2
>>> fibi(4)
3
>>> fibi(5)
5
>>> fibi(6)
8
>>> fibi(7)
13
>>>
>>>
>>>
>>> fibi2(0)
0
>>> fibi2(1)
1
>>> fibi2(2)
1
>>> fibi2(3)
2
>>> fibi2(4)
3
>>> fibi2(5)
5
>>> fibi2(6)
8
>>> fibi2(7)