Problem Writing Files

[Chris Gonnerman]

----- Original Message ----- 
From: "Roger Jones" <rmj at slac.stanford.edu>


> I am using ActiveState Python 2.1 under Windows NT  and after opening a
> file with:
> 
> afile=('test.dat','w')
> afile.write('some random test text')
> afile.read()

This surely is not a screen capture from an actual session or a sample
of an actual script... the first line is obviously wrong, as it assigns
a tuple of ('test.dat', 'w') to afile rather than opening a file.  It 
would correctly be:

    afile = open('test.dat', 'w')

Next, you write some data without a line ending (did you intend that?)
and then switched to using .read() on the file handle without further 
action.  Since you just did a write, the file pointer is at EOF, and 
assuming it's OK to follow a .write() with a .read() you should get a
null (empty) string.

I don't know about NT but under many Unixoid OS's you must have an 
intervening .seek() call between the .write() and .read() (including
of course a .rewind() call as it is basically an alias to .seek()).

Further the file mode 'w' should be 'w+' if you intend to both write
and read on the same stream.

Chris Gonnerman -- chris.gonnerman at newcenturycomputers.net
http://newcenturycomputers.net