One step list operation in Python

Question

I have a list A. I am generating a new list by adding 1 to every element of the previous list and at the end, getting a combined list B+C+D. Is there a one step way to do this?

A=[12,8,4,0]
B=[i+1 for i in A]
C=[i+1 for i in B]
D=[i+1 for i in C]
print(B+C+D)

The current and expected output is

[13, 9, 5, 1, 14, 10, 6, 2, 15, 11, 7, 3]

Asked By: rajunarlikar123

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Source

Answer 1

You can do it like this:

[i+j for i in range(1, 4) for j in A]

This produces:

[13, 9, 5, 1, 14, 10, 6, 2, 15, 11, 7, 3]

It can also be done with itertools.product, but in this case I don’t think it buys you much:

[i+j for i, j in itertools.product(range(1, 4), A)]

Answered By: Tom Karzes

Answer 2

You can also use numpy arrays:

A = np.array([12,8,4,0])
sol = np.concatenate((A+1, A+2, A+3))

The output is [13, 9, 5, 1, 14, 10, 6, 2, 15, 11, 7, 3] as expected.

Answered By: nonlinear

Answer 3

with walrus operator :=, you can achive this as

A=[12,8,4,0]
result = (B:= [i+1 for i in A]) + (C:= [i+1 for i in B]) + (D:= [i+1 for i in C])
print(result)

output

[13, 9, 5, 1, 14, 10, 6, 2, 15, 11, 7, 3]

Answered By: sahasrara62

One step list operation in Python

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