循环 python 列表中的元素至少一次

Question

So I have a simple piece of code:

class Player:
    def __init__(self):
        self.score = 0

players = [Player() for _ in range(10)]

Now I want to:

• Iterate the players in the list indefinitely
• Skip players with a negative score

from itertools import cycle

loop = cycle(players)
loop = filter(lambda player: player.score >= 0, loop)

• Stop the iteration when there is only one player left with a positive score
• Or when there are two or more players with a positive score, every one of them has been iterated at least once and each of them has an equal score

I have a problem with these conditions and I don't know how to bite them.

Answer 1

Solution 1

Here's a solution using mostly itertools .

import itertools

positive_players = lambda : filter(lambda player: player.score >= 0, players)

loop = itertools.cycle(positive_players())

if len(list(positive_players())) <= 1:
    loop = positive_players()

if len(set([p.score for p in positive_players()])) <= 1:
    loop = positive_players()

Some tests:

• 3 players, all have score zero: stops after one loop.
• 3 players with scores [0, 42, 0]: continues forever
• 3 players with scores [-1, 42, -2]: stops after printing the one positive player.

Solution 2

Here's an alternative solution, using a generator.

def loop_players(players): 
    inx = 0
    positive_count = 0
    positive_scores = set()
    while True: 
        p = players[inx]
        inx += 1
        if p.score < 0: 
            continue 
        positive_count += 1
        positive_scores.add(p.score)
        yield p 
        if inx == len(players):
            inx = 0
            if positive_count < 2: 
                break 
            if len(positive_scores) < 2:
                break