## Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

### Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

PLUS

# Make a function name first_and_last_4 that accepts an iterable and returns the first 4 and last 4 items in the iterable.

What's wrong with my code?

def first_4(x): return x[0:4]

def odds(x): return x[1::2]

def last_4(x): return x[-4:]

def first_and_last_4(x): return first_4.extend(last_4)

## 1 Answer

MOD

Three errors with the function `first_and_last_4()`.

• The functions `first_4()` and `last_4()` need to be passed arguments:
• `extend()` only works on lists and not on strings, so if a string iterable were passed to `first_and _last_4()` it would fail with an `AttributeError: str has no attribute extend`
• If passed an actually list, `extend()` operates on a list "in place", that is the output of `first_4`, which would be a list, is assigned to a temporary unnamed variable. Then extend alters this variable in place, but does not return a value. There is no value to be returned.

Ignoring the string input issue (not sure if you are asking about that aspect), see updated code below:

```def first_4(x):
return x[0:4]

def odds(x):
return x[1::2]

def last_4(x):
return x[-4:]

def first_and_last_4(x):
result = first_4(x)
result.extend(last_4(x))
return result
```

or alternatively, just add the resultant parts:

```def first_and_last_4(x):
return first_4(x) + last_4(x)
```

This would be calling a method on a function/object, not a string:

```def first_and_last_4(x):
return first_4.extend(last_4)
```

Also, Kitty Wan, I think your `odds` function isn't returning the correct result, since lists in Python begin with a zero index.