__author__ = 'ZHHT'
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import os
f = open("test1","r")
# #
# f.write("你好啊，我在这里等着你，这里真的很不错。")
sstr = f.read(2)
print(sstr)
f.seek(7,1)
sstr = f.read()
print(sstr)
f.close()
"C:\Program Files\Python35\python.exe" D:/python3.5-14/练习4.py
你好
Traceback (most recent call last):
File "D:/python3.5-14/练习4.py", line 12, in <module>
f.seek(7,1)
io.UnsupportedOperation: can't do nonzero cur-relative seeks
Process finished with exit code 1
照理说，按照seek()方法的格式file.seek(offset,whence)，后面的1代表从当前位置开始算起进行偏移，那又为什么报错呢？
这是因为官方文档这样说：
In text files (those opened without a b in the mode string), only seeks relative to the beginning of the file are allowed (the exception being seeking to the very file end with seek(0, 2)).，
在文本文件中，没有使用b模式选项打开的文件，只允许从文件头开始计算相对位置，从文件尾计算时就会引发异常。将 f=open("aaa.txt","r+") 改成
f = open("test1","rb") 就可以了
改正后的代码如下图：
__author__ = 'ZHHT'
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import os
f = open("test1","rb")
# #
# f.write("你好啊，我在这里等着你，这里真的很不错。")
sstr = f.read(2)
print(sstr)
f.seek(7,1)
sstr = f.read()
print(sstr)
f.close()