I need to find the distance of each duplicated letter

Question

from itertools import pairwise

l_h = []
l_r = []
for index, elem  in enumerate("THISISTHEARHGRAYR"):
    if elem == "R":
        l_r.append(index)
    if elem == "H":
        l_h.append(index)

H = [b - a for a, b in pairwise(l_h)]
R = [b - a for a, b in pairwise(l_r)]
print(H,R)[enter image description here][1]

And I 1: https://i.sstatic.net/dCMC5.png If i run this code I get error cannot import name 'pairwise' from 'itertools'

Answer 1

It looks like your version of itertools does not have the pairwise function. You can check its available functions in the docs (select Python version in the upper left corner).

I suggest creating your own implementation of pairwise, I found this one to work well.

Code and output:

from itertools import tee

def pairwise(iterable):
    a, b = tee(iterable) # Note that tee is from itertools
    next(b, None)
    return zip(a, b)

l_h = []
l_r = []
for index, elem in enumerate("THISISTHEARHGRAYR"):
    if elem == "R":
        l_r.append(index)
    if elem == "H":
        l_h.append(index)

# Added -1 to count letters BETWEEN duplicates
H = [ b - a - 1 for a, b in pairwise(l_h) ]
R = [ b - a - 1 for a, b in pairwise(l_r) ]

print(H, R)

outputs

[5, 3] [2, 2].

Also, upgrading to Python 3.10 should work (I have not tested this).