# 人工智能课程 05：Python 3 标准库教学示例
# 无外部网络调用；修改输入后可观察结果。
facts = {'已通电', '不制冷'}
rules = [({'已通电', '不制冷'}, '需检查'), ({'需检查'}, '人工检修')]
changed = True
while changed:
    changed = False
    for premises, conclusion in rules:
        if premises <= facts and conclusion not in facts:
            facts.add(conclusion)
            changed = True
print('人工检修' in facts)