collections.deque使用

# 导入队列
from collections import deque


def search(lines, pattern, history=5):
    # 固定长度的队列
    pre_lines = deque(maxlen=history)  # 新的元素加入，如果队列已满，最老的元素会自动被移除
    for line in lines:
        if pattern in line:
            pre_lines.append(line)
            yield line, pre_lines


def dequeDemo():
    p = deque()
    p.append('a')
    print(p)
    p.append('b')
    print(p)
    p.appendleft('a1')
    print(p)
    p.pop()
    print(p)
    p.popleft()
    print(p)


if __name__ == '__main__':
    """
    文本的内容如下：
    a b c python d
    e
    f g h e python
    j k l m python n
    o p python q r
    s1 t python u
    s2 t python u
    s3 t python u
    """
    with open(r'./dequedemo.txt') as f:
        for line, pre_lines in search(f, 'python'):
            for pl in pre_lines:
                print(pl, end='')
            print('line=', line, end='')
            print('-' * 20)

    dequeDemo()