"""

n = [3, 5, 7]

def double_list(x):

for i in range(0, len(n)):

x[i] = x[i] * 2

return x

print double_list(n)

"""

the error i get is: Oops, try again. double_list([0, 1]) resulted in an error: list index out of range

whats wrong with this code?

# 13/18

**rydan**#3

on this line

`for i in range(0, len(n)):`

you are using the length of the list n you created outside the method which means that no matter the list you pass the range will always be form 0 to 2. to correct it you have to do

`for i in range(0, len(x)):`

i've done that and now the error is Oops, try again. double_list([0, 1]) returned [0, 1] instead of [0, 2]....i really cant figure out whats wrong with this piece of code

**veneoveo**#5

```
n = [3, 5, 7]
def double_list(x):
for i in range(0, len(x)):
x[i] = x[i] * 2
return x
print double_list(n)
```

this worked for me.

the len(x) seems to be only problem in your case as rydan previously mentioned. try this and report back. hope u figure it out

Mine keep saying double_list not defined help!

n = [3, 5, 7]

def double_list(x):

for i in range(0, len(x)):

x[i] = x[i] * 2

return x

print double_list(n)

**ryzok**#9

Your code is correct!

But you have to take care on the indentation:

for i in range(0, len(x)):

--------x[i] = x[i] * 2

return x

FOR and RETURN have to be on the same indentation level!!

Hope this is helpful

**mortjan**#10

Thanx this was helpful. But there is still one thing I don’t understand quite well…

Why has the FOR and Return to be on the same indentation?

**srodr008**#11

I had the same question. If I’m understanding this thread (link below) correctly it’s because the *for* loop will continue forever unless you tell it to end by using the *return*. Because *return* is directly related to *for* it needs to be on the same ‘plane’ or indentation.

(https://discuss.codecademy.com/t/unable-to-understand-the-use-of-return/4929/2?u=srodr008)