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Start your free trial###### Mikaela Land

**Python Web Development**Techdegree Student 2,324 Points

# Slice Functions: Local variable error

In the odds function I keep getting:

UnboundLocalError: local variable 'odds_only' referenced before assignment

Not sure how to fix it. I keep trying to change things around to test it but I've got nothing. I got it to work once but it stopped working the second time.

Any ideas?

```
def first_4(lst):
return lst[:4]
def first_and_last_4 (lst2):
first = lst2 [:4]
last = lst2 [-4:]
both = first + last
return both
def odds (num):
if len(num) % 2 == 0:
odds_only = num [1::2]
return odds_only
```

## 1 Answer

###### Alexander Davison

65,468 PointsI think you are a bit lost. The `odds`

function takes in an iterable still, not a number. (It seems that you believe that it takes in an iterable.)

The problem is asking to return an iterable which has all of the __odd indexed__ values from the passed in iterable.

For instance, if I pretended I was within the Python shell:

```
>>> odds([1, 2, 3, 4, 5])
[2, 4]
>>> odds('abcdefg')
['b', 'd', 'f']
>>> odds((1, 2, 3))
[2]
```

Here's my solution to this problem:

*(Let's call the input iterable iter and the output iterable result_iter)*

- Go through every number from zero to N-1, where N is
`len(iter)`

. Let's call the "current number"`i`

. - If
`i`

is odd, add to`result_iter`

`iter[i]`

. (Because`i`

is an index, not the item itself) - Return
`result_iter`

.

Implemented in code, it may look somewhat like this:

```
def odds(iter):
result_iter = []
for i in range(len(iter)):
if i % 2 != 0:
result_iter.append(iter[i])
return result_iter
```

Simpler way for the Pythonista:

```
def odds(iter):
return [iter[i] for i in range(len(iter)) if i % 2 != 0]
```

I hope this helps!

**Happy coding!** *~Alex*

## Mikaela Land

Python Web DevelopmentTechdegree Student 2,324 Points## Mikaela Land

Python Web DevelopmentTechdegree Student 2,324 PointsThanks. I think I get it. I just have a question: why did you add range? Wouldn't that imply the list is just numbers? What's its purpose in the code?