在 Python 中使用迭代器创建无限随机游走

Question

I have a practice problem concerning random walks:

So far my code looks like this:

import random
import itertools
p = [0,0]

def random_walk():
    yield p
    for _ in itertools.count(0,1):
        sign = random.randrange(-1, 2,2)
        cord = random.randint(0,1)
        p[cord] += sign
        yield p

However, when I run it nothing happens. I assume it runs too many times too quickly to actually yield anything. Is there any way to fix this so it outputs a sequence like the one in the problem text? Just to let you know, I am taking an introductory course to Python focused on scientific applications so my general knowledge of programming, in general, is very limited. Later on in the exercise, I am supposed to use itertools.islice to generate a finite path but I need this to work first. Any help will be much appreciated!

Answer 1

You have to use your generator to see the results (for example in a for loop). Also, a generator should return individial values, not the accumulated list of values so far:

import random
def random_walk():
    x = y = 0
    offsets = [ (0,1),(0,-1),(1,0),(-1,0) ]
    while True:
        yield (x,y)
        dx,dy = random.choice(offsets)
        x,y   = x+dx, y+dy

output:

from itertools import islice
print(*islice(random_walk(),10))

(0, 0) (-1, 0) (-1, -1) (0, -1) (0, 0) (-1, 0) (-1, -1) (-2, -1) (-2, -2) (-2, -1)

proof that it is infinite:

for point in random_walk(): print(point, end=" ")

(0, 0) (-1, 0) (-1, -1) (-1, -2) (0, -2) (0, -3) (0, -4) (-1, -4) (-2, -4) (-3, -4) (-4, -4) (-4, -5) (-5, -5) (-4, -5) (-3, -5) (-3, -6) (-4, -6) (-4, -7) (-4, -6) (-3, -6) (-3, -7) (-4, -7) (-5, -7) (-4, -7) (-5, -7) (-5, -6) (-4, -6) (-3, -6) (-4, -6) ...

note you have to interrupt this loop with control-C because it is infinite