[Tutor] Re: Can you modify every nth item in a list with a single assignment?

[Andrei]

Alan Gauld wrote:

>> >>> b = [1, 2, 3, 4, 5, 6, 7, 8, 9]
>> >>> [ item in range(2, len(b), 3) and 2*b[item] or b[item] for item
> in
>>range(0, len(b))]
> 
> Very clever, but it is still two lines and much more

One line, but wrapped in an unfortunate manner by Mozilla.

> complicated than the explicit loop version:
> 
> b = [1, 2, 3, 4, 5, 6, 7, 8, 9]
> for n in range(2,len(b),3): b[n] *= 2
> 
> Alan G.

Duh, so obvious and I didn't see it (I always start a new line after 
":"). On the other hand, the list comprehension could be used to change 
different items in different ways (e.g. every third item times 2, the 
other ones plus 2) in a single, extremely long and unmaintainable line.
I liked Alfred Milgrom's solution too.

Andrei

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