[Tutor] modification to a list

[Alan Gauld]

On 22/04/2020 16:59, Subhash Nunna wrote:

> Please try this:
> 
> def skip_elements(elements):
>     new_list = [ ]
>     a = len(elements)+1

You don't want to add one. Just use len()

>     if a==1:
>         return new_list

a==1 implies an empty list using your code above.

>     else:
>         for i in range(0, a):

This will push index past the end of the list.
If the list is [1,2,3] then len() returns 3 and a is set to 4
Now range(0,4) returns [0,1,2,3]
But there is no index 3.

>             if i%2==0:
>                 new_list.append(elements[i])
>         return new_list

It is because of the difficulty in getting indexes right
that we prefer to use the foreach style of processing
in Python:

for item in elements

And if you really need the index(rare) you can use enumerate:

for index,item in enumerate(elements):

These guarantee never to over-run your collection.


-- 
Alan G
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