Bummer, should this not be 46,47,48,49?

Question

As I have struggled with the answer to the slice challenge, I decided to make sure I got the correct last 4.  And this is what it gave me: 
Bummer! first_4() didn't return the right output. It returned [7, 8, 9, 10] instead of [1, 2, 3, 4].
I did not think we had to make the range first? Did I ASSume wrong?  As I thought the range was 0->49.
```slices.py
def first_4(iterable):
  return iterable[-4:]
```

Juan Martin · Answer

Hello my friend, remember that when you're slicing, the thing goes as this:
[start:stop:step]
With [-4:], it's will start from the position/index "-4", and that's 4 steps from the end, to the end of the list.
For example: 
If the end is number 10, then number 10 = position/index -1, number 9 = position/index -2, number 8 = position/index -3, number 7 = position/index -4. So it'll start from the number seven.
The easiest way to solve this is doing it like this:
python
def first_4(iterable):
  return iterable[:4]

Also, while slicing, when you delimit the "stop" that'll be until that position/index, but not including it, so [:4] will be until position/index 4, but it'll not include it, and will go like this:
position/index = 0, position/index = 1, position/index = 2, position/index = 3 (doesn't include the position/index =  4)
The resulting list (if it starts with number 1) will be this:
python
[1, 2, 3, 4]

Note: The challenge says that you're looking for the "first 4", not the "last 4"
Hope this helps :)

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Rune Larsen

Rune Larsen

Bummer, should this not be 46,47,48,49?

1 Answer

Juan Martin

Juan Martin