Hello,
I'm trying to write exception-handling code that is OK in the
presence
of unicode error messages. I seem to have gotten all mixed up and
I'd
appreciate any un-mixing that anyone can give me.
I'm used to writing code like this.
class myException(Exception):
pass
fn='README'
try:
f=open(fn,'r')
except Exception, err:
mesg='unable to open file'+fn+': '+str(err)
raise myException, mesg
But what if fn is non-ascii? The following code raises the
dreaded (to me) UnicodeEncodeError.
class myException(Exception):
pass
def fcnCall():
fn=u'a\N{LATIN SMALL LETTER O WITH DIAERESIS}k'
try:
# was: f=open(fn,'r')
2/0 # just substitute something that will raise an
exception
except Exception, err:
mesg='unable to open file '+fn+': '+str(err)
raise myException, mesg
try:
fcnCall()
except Exception, err:
print 'trouble calling fcnCall: '+str(err)
Maybe my trouble is the "str()", which is supposed to return a
regular
string? (BTW, unicode() makes no difference, and help(BaseException)
didn't give me any inspirations.) So I looked for an end-around past
the
str() call.
As I understand lib/module-exceptions.html, "For class
exceptions, [err] receives the exception instance. If the exception
class is derived from the standard root class BaseException, the
associated value is present as the exception instance's args
attribute.", I should be able to get the string out of err.args. Sure
enough, putting the above text into test.py and changing str(err)
to repr(err.args) yields this.
$ python test.py
trouble calling fcnCall: (u'unable to open file a\xf6k: integer
division or modulo by zero',)
so that changing the above repr(err.args) to err.args[0] gives the
desired result.
$ python test.py
trouble calling fcnCall: unable to open file aök: integer division
or modulo by zero
(In case this doesn't show up as I intended on your screen, I see an
o with a diaeresis in the filename.)
But the documentation "This may be a string or a tuple containing
several
items of information (e.g., an error code and a string explaining the
code)." gives me no reason to believe that all exceptions have the
desired
unicode string as the 0-th element of the tuple. I confess that I'm
unable
to confidently read exceptions.c .
No doubt I've missed something (I googled around the net and on this
group
but I didn't have any luck). I'd be grateful if someone could show
me
striaght.
Thanks,
Jim
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