python模块之linecache

# -*- coding: utf-8 -*-
#python 27
#xiaodeng
#python模块之linecache

import linecache
'''
>>> help(linecache)
Help on module linecache:
FUNCTIONS
    checkcache = extended_linecache_checkcache(filename=None, orig_checkcache=<function checkcache>)
        Extend linecache.checkcache to preserve the <pyshell#...> entries

        Rather than repeating the linecache code, patch it to save the
        <pyshell#...> entries, call the original linecache.checkcache()
        (skipping them), and then restore the saved entries.

        orig_checkcache is bound at definition time to the original
        method, allowing it to be patched.

    clearcache()
        Clear the cache entirely.

    getline(filename, lineno, module_globals=None)

DATA
    __all__ = ['getline', 'clearcache', 'checkcache']
'''

#从名为filename的文件中得到第lineno行。这个函数从不会抛出一个异常–产生错误时它将返回”（换行符将包含在找到的行里）。

#linecache.getline(filename,lineno)
#查找特定行（第一行）的数据，返回一个字符串
filename='1.txt'
re= linecache.getline(filename,1)
print re.strip()#因为本身带有换行符

#得到所有行数据，返回一个list
re= linecache.getlines(filename)
print re

#获取多少行的数据
re= linecache.getlines(filename)[0:4]
print re

#更新文件名为filename的缓存。如果filename文件更新了，使用这个函数可以更新linecache.getlines(filename)返回的列表
linecache.updatecache(filename)

#清理缓存
linecache.clearcache()