# Python Code Challenges: Lists (Advanced)

Hey everyone!
During the exercise n° 4 of the Python Code Challenges: Lists (Advanced), I found probably another solution to solve the exercise in a more easier way (I’m a newcomer to Python3, so I’m not so sure ).
The original solution was:

``````def double_index(lst, index):
# Checks to see if index is too big
if index >= len(lst):
return lst
else:
# Gets the original list up to index
new_lst = lst[0:index]
# Adds double the value at index to the new list
new_lst.append(lst[index]*2)
#  Adds the rest of the original list
new_lst = new_lst + lst[index+1:]
return new_lst

print(double_index([3, 8, -10, 12], 2))
``````

And my solution is:

``````def double_index(lst, index):
if index + 1 <= len(lst):
lst[index] *= 2
return lst

print(double_index([3, 8, -10, 12], 2))
``````

Someone can review this few lines of code?
Thank you very much in advance.

Have a nice day

Your solution is certainly quicker (and shorter); however it does modify the original list (the function’s input). This is sometimes considered bad practise, as in the future, you may want to access this list. That’s the reason CC’s solution goes about creating a whole new list. As for which one is better, that really depends on how you prefer to code…

1 Like

I always struggle with this. Even if we do not want to modify the list, I would do something like:

``````def double_index(lst, index):
lst = lst.copy()
if index + 1 <= len(lst):
lst[index] *= 2
return lst

x = [3, 8, -10, 12]
print(double_index(x, 3))
print(x)
``````

So its clear that we are copying the list. The slicing would confuse me if I had to look at after three months

or you could argue (depending on the requirements), to add another parameter, like so for example:

``````def double_index(lst, index, modify = True):
if not modify:
lst = lst.copy()
if index + 1 <= len(lst):
lst[index] *= 2
return lst

x = [3, 8, -10, 12]
print(double_index(x, 3))
print(x)
``````
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Fair, fair. I think the lesson is partly geared towards list slicing practise, but very true.

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Can someone tell me is anything wrong in it ?
I mean this code also do what was asked .

def double_index(lst,index): if index <= len(lst)+1: lst.pop(index) lst.insert(index,index*2) return lst else: return lst print(double_index([3, 8, -10, 12], 2))

Hello @ajax6834969237, welcome to the forums! I believe that the exercise wants you to double the element at a specific index, not just double the index:

``````print(double_index([1,2,3,4], 2))
#should print [1,2,6,4]
``````

Thanks a lot …
it is right now ?

def double_index(lst,index): if index <= len(lst)+1: lst.insert(index,lst[index]*2) lst.pop(index+1) return lst else: return lst print(double_index([3, 8, -10, 12], 2))

That seems to be correct; good job!

1 Like