每天CookBook之Python-062

• 定义带特殊状态的生成器函数

from collections import deque


class linehistory:
    def __init__(self, lines, histlen=3):
        self.lines = lines
        self.history = deque(maxlen=histlen)

    def __iter__(self):
        for lineno, line in enumerate(self.lines, 1):
            self.history.append((lineno, line))
            yield line

    def clear(self):
        self.history.clear()

with open('passwd.txt') as f:
    lines = linehistory(f)
    for line in lines:
        if 'python' in line:
            for lineno, hline in lines.history:
                print('{}:{}'.format(lineno, hline))

f = open('passwd.txt')
lines = iter(f)
print(next(lines))
print(next(lines))
print(next(lines))
print(next(lines))

out

11:passwd

12:passwd

13:python3333

passwd

passwd

passwd

passwd