collections.deque 列队实现保留N个记录

file:
    1  sh startup.sh
    2  exit
    3  cd /data/tomcat6/bin/
    4  ps -ef |grep tomcat
    5  top
    6  ps -ef |grep tomcat
    7  kill -9 12621
    8  ps -ef |grep tomcat
    9  sh startup.sh
   10  exit
   11  cd /data/tomcat6/bin/
   12  ps -ef |grep tomcat
   13  kill -9 24844
   14  ps -ef |grep tomcat
   15  sh startup.sh
   16  exit
   17  ps -ef |grep tomcat
   18  cd /data/tomcat6/bin/
   19  kill -9 23973
   20  ps -ef |grep tomcat

例:

from collections import deque
def search(line,pattern,history=5):
    previous_lines = deque(maxlen=history)
    for li in line:
        if pattern in li:
            yield li,previous_lines
        previous_lines.append(li)

if __name__ == '__main__':
    "在 file 文件中,查找 'sh startup.sh' 字符串, 并且显示查找到'sh startup.sh' 字符串之前的5个记录"
    with open('file') as f:
        for line,previlnes in search(f,'sh startup.sh',5):
            for piline in previlnes:
                print(piline)
            print(line)
            print('_' * 20)