[Python-Dev] file()

Georg Brandl g.brandl at gmx.net
Mon Jun 12 21:11:05 CEST 2006

Guido van Rossum wrote:
> Yup, although it's a change in behavior that would need to be studied
> carefully for backwards incompatibilities. Usually it's given as a
> constant, so there won't be any problems; but there might be code that
> receives a mode string and attempts to test its validity by trying it
> and catching IOError, such code would have to be changed.
> --Guido
> On 6/12/06, Kristján V. Jónsson <kristjan at ccpgames.com> wrote:
>> I notice that file() throws an IOError when it detects an invalid mode
>> string.  Wouldn't a ValueError be more appropriate?

The situation is even more complex with the current trunk. open() raises
ValueError if it detects an invalid the mode string, such as universal
newline mode and a writable mode combined (the definition of
what is invalid has been made stricter, the mode string now must begin
with r, w, a or U), but it raises IOError if the OS call to fopen() fails
because of an invalid mode string. This might need unification.


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