[Python-Dev] open() mode is lax

[Tim Peters]

[Greg Ewing]
> I've just noticed that (in 2.3.4) open() seems to accept
> just about anything after the first character of the
> mode argument:
>
> Python 2.3.4 (#1, Jun 30 2004, 16:47:37)
> [GCC 3.2 20020903 (Red Hat Linux 8.0 3.2-7)] on linux2
> Type "help", "copyright", "credits" or "license" for more information.
>  >>> f = open("DU", "rqwerty")
>  >>>

Yes.  That's because virtually all C libraries accept just about
anything in the mode string, so that code using mode-string extensions
specific to other platforms doesn't just blow up.  Python passes the
mode string on to the platform C, and complains if and only if the
platform C complains.