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.

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Re: writing some lines after reading goes wrong on windows？

[harveysthomas]

If you are opening a file for read and write access use rb+ or wb+.
Seeking and subsequent read/write will then work fine. Without the b,
 Windows opens the file in its text mode. Don't seek on files opened
in text mode.

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