Misleading error message when opening a file (on Windows XP SP 2)

[Claudio Grondi]

Tim Peters wrote:
> [Claudio Grondi]
> 
>> Here an example of what I mean
>> (Python 2.4.2, IDLE 1.1.2, Windows XP SP2, NTFS file system, 80 GByte
>> large file):
>>
>>  >>> f = file('veryBigFile.dat','r')
>>  >>> f = file('veryBigFile.dat','r+')
>>
>> Traceback (most recent call last):
>>    File "<pyshell#1>", line 1, in -toplevel-
>>      f = file('veryBigFile.dat','r+')
>> IOError: [Errno 2] No such file or directory: 'veryBigFile.dat'
>>
>> Is it a BUG or a FEATURE?
> 
> 
> Assuming the file exists and isn't read-only, I bet it's a Windows
> bug, and that if you open in binary mode ("r+b") instead I bet it goes
> away (this wouldn't be the first large-file text-mode Windows bug).

I knew already that 'r+b' fixes it. Yes, you have won the bet :) .

I suppose, like you do, that because there is a difference between text 
and binary files on Windows and the text files are e.g. opened being 
buffered using a 32-bit buffer pointer, this fails on too large NTFS files.

I could also imagine that Python tries to buffer the text file and fails 
because it uses the wrong pointer size when asking Windows for the 
content. I have not yet looked into the C-code of Python - any hint 
which file I should take a closer look at?
Just curious to see for myself, that the bug is on the Windows side.

Claudio Grondi