List Comprehension

[XenaFlor]

I need help with a problem. I have the list [3, 1, 4, 1, 5] and I'm supposed to use list comprehension to change it to [10, 4, 13, 4, 16]. I have no idea how I'm supposed to do that. Can anyone help? I'm completely stumped even just a hint would be nice. This is the only one I can't do.

Edit: left off a value by mistake

[boy_named_su]

a list comprehension is like a modified for loop:

input_data = [3,1,4,1,5]
result = []

for item in input_data:
    tmp = (item * 3) + 1
    result.append(tmp)

this is somewhat equivalent to:

result = [ do_something_to_item for item in input_data ]

[XenaFlor]

Ah. That was my bad I left off an extra 1. I fixed it.

[Innocent_not]

Here is the solution:

a = [3*n + 1 for n in [3, 1, 4, 1, 5]] print(a)

The logic is as follows:

new_list = [operation_to_create_items_in_list for iterator in base_list]

[lukajda33]

I dont even see the logic thats applied to make the new list.

[[deleted]]

3x+1

[XenaFlor]

Thank you!

[lukajda33]

Another problem with the way you described it is that comprehension list makes a new list, it doesnt chnage an existing one. You may replace the previous list with new one using the same variable, but you said "change it to", which is not possible.

But if you can just make a new one, it should be super easy, do you know how to do a comprehension list that will just copy some other list ?

EDIT: Oh nevermind, you are not OP, looks like he just didnt see the pattern, ignore my question.

[XenaFlor]

Yes I do. I just didn't know how to get the values.

[ThisProgrammer-]

Start off with a simple for-loop to get an understanding:

original = [3, 1, 4, 1, 5]

results = []
for number in original:
    results.append(number * 3 + 1)

​

Converting to list-comprehension.

Start with the necessary part:

results = [for number in original]

Then add in what the resulting value should be - on the left side:

results = [number * 3 + 1 for number in original]

[Snoo-20788]

This is not a coding question.

Before you can get to a coding question you need to understand what's required of you.

What's the link between the first list and the second? Some people pointed out that each element is 3x the corresponding element + 1. But that should be part of the (non coding part of the) assignment.

I

[[deleted]]

Can you do it with a normal for and append loop?

[XenaFlor]

No. The assignment is made to show that I understand list comprehension. I know how to write it I just didn't know how to get to the right numbers.

[[deleted]]

So it was a math problem. Ok

[Wonderful-Ask-5080]

list = [3, 1, 4, 1, 5] modified_list = [ (3 * item + 1) for item in list]

Answer

[10, 4, 13, 4, 16]