writing some lines after reading goes wrong on windows？

[yichao.zhang]

Hi all
I can not write anything if I have read something.
the code as:


Python 2.4.3 (#69, Apr 11 2006, 15:32:42) [MSC v.1310 32 bit (Intel)]
on win32
IDLE 1.1.3
>>> a=open('d:\\a','r+')
>>> a
<open file 'd:\a', mode 'r+' at 0x00A147B8>
>>> a.read()
'11\n22\n33\n'
>>> a.seek(0)
>>> a.read(1)
'1'
>>> a.write("a")
>>> a.seek(0)
>>> a.read()
'11\n22\n33\n'                   # it fails to write after reading

>>> a.seek(0)
>>> a.write("a")
>>> a.seek(0)
>>> a.read()
'a1\n22\n33\n'                  # it writes fine at the beginning of
the file
>>>

it fails to write "a". but on my debian box, it works fine.
the code on debian as:
 Python 2.3.5 (#2, Sep  4 2005, 22:01:42)
[GCC 3.3.5 (Debian 1:3.3.5-13)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> a=open('/a','r+')
>>> a
<open file '/a', mode 'r+' at 0x4019dd60>
>>> a.read()
'11\n22\n33\n'
>>> a.seek(0)
>>> a.read(1)
'1'
>>> a.write("a")
>>> a.seek(0)
>>> a.read()
'1a\n22\n33\n'
>>> 

What's wrong here? is this a bug on windows platform.