Why 'r' mode anyway? (was: Re: Pickled text file causing ValueError (dos/unix issue))

[Tim Peters]

[Irmen de Jong]
> I've been wondering why there even is the choice between binary mode
> and text mode. Why can't we just do away with the 'text mode' ?
> What does it do, anyways? At least, if it does something, I'm sure
> that it isn't something that can be done in Python itself if
> really required to do so...

It's not Python's decision, it's the operating system's.  Whether
there's an actual difference between text mode and binary mode is up
to the operating system, and, if there is an actual difference, every
detail about what the difference(s) consists of is also up to the
operating system.  That differences may exist is reflected in the C
standard, and the rules for text-mode files are more restrictive than
most people would believe.

On Unixish systems, there's no difference.  On Windows boxes, there
are conceptually small differences with huge consequences, and the
distinction appears to be kept just for backward-compatibility
reasons.  On some other systems, text and binary files are entirely
different kinds of beasts.

If Python didn't offer text mode then it would be clumsy at best to
use Python to write ordinary human-readable text files in the format
that native software on Windows, and Mac Classic, and VAX (and ...)
expects (and the native format for text mode differs across all of
them).  If Python didn't offer binary mode then it wouldn't be
possible to use Python to process data in binary files on Windows and
Mac Classic and VAX (and ...).  If Python used its own
platform-independent file format, then it would end up creating files
that other programs wouldn't be able to deal with.

Live with it <wink>.