Mike Kent wrote:
Before I file a bug report against Python 2.5.2, I want to run this by
the newsgroup to make sure I'm not [missing something].
Good idea ;-). What you are missing is a rereading of the fine manual
to see what you missed the first time. I recommend this *whenever* you
are having a vexing problem.
I have a text file of fixed-length records I want to read in random
order. That file is being changed in real-time by another process,
and my process want to see the changes to the file. What I'm seeing
is that, once I've opened the file and read a record, all subsequent
seeks to and reads of that same record will return the same data as
the first read of the record, so long as I don't close and reopen the
file. This indicates some sort of buffering and caching is going on.
In particular, for 2.x
"open( filename[, mode[, bufsize]])
...
The optional bufsize argument specifies the file's desired buffer size:
0 means unbuffered, 1 means line buffered, any other positive value
means use a buffer of (approximately) that size. A negative bufsize
means to use the system default, which is usually line buffered for tty
devices and fully buffered for other files. If omitted, the system
default is used.2.3 "
Give open('foo.txt', 'r', 0) a try and see if it makes a difference.
There is a slight change in 3.0. "Pass 0 to switch buffering off (only
allowed in binary mode)" I presume the restriction is because 't' mode
is for automatic decoding to unicode and buffering is used for that.
tjr
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