# Wrong code for Fibonacci Bumbers, why?

Hi! For question 7, the last line of code is:

a, b = b, a+b.

I assume this is the same as writing 2 lines of code:

a = b

b = a+b

But I get another result, not the Fibonacci numbers, why?

Hey Juan,

Thank you for the good question!

As it turns out, the line of code

```
a, b = b, a+b
```

is not equivalent to

```
a = b
b = a+b
```

Let us take `a = 0`

and `b = 1`

. Performing the first line of code above would be equivalent to

```
a, b = 1, 0+1
```

Note how we are using the old values of `a`

and `b`

.

Now, if we again take `a = 0`

and `b = 1`

but this time we execute the second line of code, the operation would be equivalent to:

```
a = b = 1
b = a+b = 1+1 = 2
```

Note how, this time, we first redefine the variable `a`

and then update the variable `b`

. This is where the discrepancy comes from.

Hope this helps! Keep up the good work!

Kind regards,

365 Hristina

Got it, thanks!

Could you please clarify this more? I do not quite understand Hristina's explanation?

Elisha - this helped me to better understand:

Python Program to Print the Fibonacci Sequence (freecodecamp.org)