Python的StringIO模块和cStringIO模块

1.StringIO模块

StringIO用于像文件一样对字符串缓冲区或者叫做内存文件进行读写。

    f = StringIO()      # ready for writing

    f = StringIO(buf)   # ready for reading

    f.close()           # explicitly release resources held

    flag = f.isatty()   # always false

    pos = f.tell()      # get current position

    f.seek(pos)         # set current position

    f.seek(pos, mode)   # mode 0: absolute; 1: relative; 2: relative to EOF

    buf = f.read()      # read until EOF

    buf = f.read(n)     # read up to n bytes

    buf = f.readline()  # read until end of line ('\n') or EOF

    list = f.readlines()# list of f.readline() results until EOF

    f.truncate([size])  # truncate file at to at most size (default: current pos)

    f.write(buf)        # write at current position

    f.writelines(list)  # for line in list: f.write(line)

    f.getvalue()        # return whole file's contents as a string

在有些时候python调用shell命令或者使用socket向端口发送命令后返回一大串分行的字符串。就可以使用StringIO对这些字符串分行读写。

例如向ZooKeeper的端口发送mntr命令

import socket

s=socket.socket()
s.connect(('localhost',2181))
s.send('mntr')
data_mntr=s.recv(2048)
s.close()
print data_mntr

# python test.py 
zk_version3.4.6-1569965, built on 02/20/2014 09:09 GMT
zk_avg_latency0
zk_max_latency0
zk_min_latency0
zk_packets_received335
zk_packets_sent334
zk_num_alive_connections1
zk_outstanding_requests0
zk_server_statefollower
zk_znode_count17159
zk_watch_count0
zk_ephemerals_count1
zk_approximate_data_size6666471
zk_open_file_descriptor_count27
zk_max_file_descriptor_count102400

data_mntr返回的数据就是一个string buffer，如果需要对每行数据进行读写，就需要像文件那样使用readline()或者readlines()

#!/usr/bin/python
import socket
from StringIO import StringIO
s=socket.socket()
s.connect(('localhost',2181))
s.send('mntr')
data_mntr=s.recv(2048)
s.close()

h=StringIO(data_mntr)

print h.readline()
print h.readlines()

# python test.py 
zk_version3.4.6-1569965, built on 02/20/2014 09:09 GMT

['zk_avg_latency\t0\n', 'zk_max_latency\t0\n', 'zk_min_latency\t0\n', 'zk_packets_received\t347\n', 'zk_packets_sent\t346\n', 'zk_num_alive_connections\t1\n', 'zk_outstanding_requests\t0\n', 'zk_server_state\tfollower\n', 'zk_znode_count\t17159\n', 'zk_watch_count\t0\n', 'zk_ephemerals_count\t1\n', 'zk_approximate_data_size\t6666471\n', 'zk_open_file_descriptor_count\t27\n', 'zk_max_file_descriptor_count\t102400\n']

2.cStringIO模块

cStringIO模块和StringIO模块功能类似。不过这个模块是用C语言编写的。

将以上的

from StringIO import StringIO

直接换成

from cStringIO import StringIO

参考文章：

https://docs.python.org/2.6/library/stringio.html