Calculate list of distances

Question

I have a list:

my_list = [A,B,G,X,F,D]

Each letter on the list is some point in space (x,y).

I have a function to calculate distance between 2 points:

dist = distance(A,B)

I need to calculate list of distances between neighbouring points on the list:

list_of_distances = [distance(A,B), distance(B,G), distance(G,X), distance(X,F), distance(F,D)]

The question is: How to do it iteratively in most pythonic way?

Does this answer your question? [Rolling or sliding window iterator?](https://stackoverflow.com/questions/6822725/rolling-or-sliding-window-iterator). Using a standard sliding window, you can simply compute `[distance(a, b) for a,b in windows(my_list, 2)]` — Brian61354270, Mar 19 '20 at 18:02
`dist = [distance(my_list[i], mylist[i+1]) for i in range(len(my_list)-1)]` — Tom Karzes, Mar 19 '20 at 18:04

kederrac · Accepted Answer · 2020-03-19T18:17:14.100

5

you could use zip built-in function:

dist = [distance(a, b) for a, b in zip(my_list, my_list[1:])]

or as suggested by @DaniMesejo:

 dist = list(map(distance, my_list, my_list[1:]))

edited Mar 19 '20 at 18:17

answered Mar 19 '20 at 18:08

kederrac

4

map can receive multiple iterables, so you can do map(distance, my_list, my_list[1:]) – Dani Mesejo Mar 19 '20 at 18:11
yes, you will mind if I add this in my answer? – kederrac Mar 19 '20 at 18:14
1

Go ahead, is fine with me – Dani Mesejo Mar 19 '20 at 18:16

score 2 · Answer 2 · answered Mar 19 '20 at 18:16

2

Just another way: [*map(distance, my_list, my_list[1:])]

Demo:

>>> my_list = [3, 1, 4, 1, 5, 9]
>>> def distance(a, b):
        return abs(a - b)

>>> [*map(distance, my_list, my_list[1:])]
[2, 3, 3, 4, 4]

answered Mar 19 '20 at 18:16

Kelly Bundy

2 Answers2