#-*- coding:utf-8 -*-
'''
Created on 2011-12-4
作者: 李昱彤
Email: liqi1031@gmail.com
'''
#open 函数可能引发IOError异常（可能文件不存在）
#seek 方法可能引发IOError异常（可能是文件长度小于给定的字节数）
#read 方法可能引发IOError异常（可能磁盘有坏扇区，或它在一个网络驱动器上，而网络刚好断了）

#import pdb
#pdb.set_trace()
filename = "d:\python27\python.exe"

#计算文件的大小
f = open(filename, "rb", 0)
fileStart = f.tell()
print "file start position: ", fileStart, "byte"
f.seek(0,2)
fileEnd =f.tell()
print "file end position: ", fileEnd, "bytes"
print "So file size is ", (fileEnd - fileStart), "bytes."

#引发seek异常
try:
    f = open(filename,"rb", 0)
    try:
        print "file pointer position is ", f.tell()
        f.seek(-26625,2)
        data = f.read(10)
        print "getting 10 bytes file content is ", data
        print "file pointer position is ", f.tell()
    finally:
        f.close()
except IOError:
    print 'IOError from f.seek() happens'

 

输出结果：

file start position:  0 byte
file end position:  26624 bytes
So file size is  26624 bytes.
file pointer position is  0
IOError from f.seek() happens