this post was submitted on 25 Jun 2024
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Why can't I append to list inside of a list comprehension? (lemmy.world)
submitted 2 months ago* (last edited 2 months ago) by librejoe@lemmy.world to c/python@programming.dev
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I'm new to programming a bit, and am learning python so I can learn flask, using the python crash course book. I was learning about list comprehension but it briefly talks about it. If I do

list[list.append(value) for value in range(1, 20)]

it doesn't work. Would this be some sort of recursive expression that is not possible?

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[–] stevedidwhat_infosec@infosec.pub 1 points 2 months ago* (last edited 2 months ago)

Not quite!

Try:

mylist = [value for value in range(1,20)]

This says I want to make mylist be a list where each element of the list (called value here) comes from doing a for loop on range, given the parameters 1, and 20.

If you want to change how each element of this list is, you do it in the first bit on “value”

So you could do

mylist = [value*5 for value in range(1,20)] //5,10,15,…,95 (not 100, because ranges go up to the last item, not including it (non-inclusive))

Etc. Hope this makes sense!

Edit: MISSING CLOSING PARENTHESIS DOH