Iterate over a ‘window’ of adjacent elements in Python

Question

This is more a question of elegance and performance rather than “how to do at all”, so I\'ll just show the code:

def iterate_adjacencies(gen, fill=0, size=2,         


        

Answer 1

I'm surprised nobody took a simple coroutine approach.

from collections import deque


def window(n, initial_data=None):
    if initial_data:
        win = deque(initial_data, n)
    else:
        win = deque(((yield) for _ in range(n)), n)
    while 1:
        side, val = (yield win)
        if side == 'left':
            win.appendleft(val)
        else:
            win.append(val)

win = window(4)
win.next()

print(win.send(('left', 1)))
print(win.send(('left', 2)))
print(win.send(('left', 3)))
print(win.send(('left', 4)))
print(win.send(('right', 5)))

## -- Results of print statements --
deque([1, None, None, None], maxlen=4)
deque([2, 1, None, None], maxlen=4)
deque([3, 2, 1, None], maxlen=4)
deque([4, 3, 2, 1], maxlen=4)
deque([3, 2, 1, 5], maxlen=4)