Re: Re-raising exceptions with modified message
On Jul 15, 2:55 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Here is a simple solution, but it depends on the existence of the args attribute that will eventually be deprecated according to the docs If you don't mind using .args, then the solution is usually as simple as: try: Thing.do(arg1, arg2) except Exception, e: e.args += (Thing.state, arg1, arg2) raise No over-engineering needed. ;) Robert Brewer System Architect Amor Ministries [EMAIL PROTECTED] -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
En Mon, 16 Jul 2007 13:50:50 -0300, fumanchu [EMAIL PROTECTED] escribió: On Jul 15, 2:55 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Here is a simple solution, but it depends on the existence of the args attribute that will eventually be deprecated according to the docs If you don't mind using .args, then the solution is usually as simple as: try: Thing.do(arg1, arg2) except Exception, e: e.args += (Thing.state, arg1, arg2) raise No over-engineering needed. ;) If you read enough of this long thread, you'll see that the original requirement was to enhance the *message* displayed by a normal traceback - the OP has no control over the callers, but wants to add useful information to any exception. Your code does not qualify: py try: ... open(a file that does not exist) ... except Exception,e: ... e.args += (Sorry,) ... raise ... Traceback (most recent call last): File stdin, line 2, in module IOError: [Errno 2] No such file or directory: 'a file that does not exist' py try: ... x = uá.encode(ascii) ... except Exception,e: ... e.args += (Sorry,) ... raise ... Traceback (most recent call last): File stdin, line 2, in module UnicodeEncodeError: 'ascii' codec can't encode character u'\xe1' in position 0: ordinal not in range(128) -- Gabriel Genellina -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
samwyse wrote: NewStyle.__name__ = old.__class__.__name__ Simple, but that does the trick! new.__dict__ = old.__dict__.copy() Unfortunately, that does not work, since the attributes are not writeable and thus do not appear in __dict__. But my __getattr__ solution does not work either, since the attributes are set to None when initialized, so __getattr__ is never called. Need to think about this point some more... Anyway, the beer is on me ;-) -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Christoph Zwerschke wrote:
But my __getattr__ solution does not work either, since the attributes
are set to None when initialized, so __getattr__ is never called.
Here is a simple solution, but it depends on the existence of the args
attribute that will eventually be deprecated according to the docs:
def PoliteException(e):
E = e.__class__
class PoliteException(E):
def __str__(self):
return str(e) + , sorry!
PoliteException.__name__ = E.__name__
return PoliteException(*e.args)
try:
unicode('\xe4')
except Exception, e:
p = PoliteException(e)
assert p.reason == e.reason
raise p
--
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Re: Re-raising exceptions with modified message
Christoph Zwerschke wrote:
Here is a simple solution, but it depends on the existence of the args
attribute that will eventually be deprecated according to the docs:
Ok, here is another solution that does not depend on args:
def PoliteException(e):
E = e.__class__
class PoliteException(E):
def __init__(self):
for arg in dir(e):
if not arg.startswith('_'):
setattr(self, arg, getattr(e, arg))
def __str__(self):
return str(e) + , sorry!
PoliteException.__name__ = E.__name__
return PoliteException()
try:
unicode('\xe4')
except Exception, e:
p = PoliteException(e)
assert p.reason == e.reason
raise p
--
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Re: Re-raising exceptions with modified message
Christoph Zwerschke wrote:
Here is a simple solution, but it depends on the existence of the args
attribute that will eventually be deprecated according to the docs:
Just found another amazingly simple solution that does neither use teh
.args (docs: will eventually be deprecated) attribute nor the dir()
function (docs: its detailed behavior may change across releases).
Instead it relies on the fact that the exception itselfs behaves like
its args tuple (checked with Py 2.3, 2.4 and 2.5).
As another twist, I set the wrapper exception module to the module of
the original exception so that the output looks more like the output of
the original exception (i.e. simply UnicodeDecodeError instead of
__main__.UnicodeDecodeError).
The code now looks like this:
def PoliteException(e):
E = e.__class__
class PoliteException(E):
def __str__(self):
return str(e) + , sorry!
PoliteException.__name__ = E.__name__
PoliteException.__module__ = E.__module__
return PoliteException(*e)
try:
unicode('\xe4')
except Exception, e:
p = PoliteException(e)
assert p.reason == e.reason
raise p
--
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Re: Re-raising exceptions with modified message
On Jul 13, 12:45 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
samwyse wrote:
TypeError: __class__ must be set to a class
Excpt ceratinly appears to be a class. Does anyone smarter than me
know what's going on here?
Not that I want to appear smarter, but I think the problem here is that
exceptions are new-style classes now, whereas Empty is an old-style
class. But even if you define Empty as a new-style class, it will not
work, you get:
TypeError: __class__ assignment: only for heap types
This tells us that we cannot change the attributes of a built-in
exception. If it would be possible, I simply would have overridden the
__str__ method of the original exception in the first place.
-- Chris
Chris, you owe me a beer if you're ever in St. Louis, or I'm ever in
Germany.
# - CUT HERE -
# Written by Sam Denton [EMAIL PROTECTED]
# You may use, copy, or distribute this work,
# as long as you give credit to the original author.
# tested successfully under Python 2.4.1, 2.4.3, 2.5.1
On Jul 5, 2007, at 8:53 am, Christoph Zwerschke [EMAIL PROTECTED]
wrote:
What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)? Let's say for simplicity I just want to add sorry to
every exception message.
Here is an example of typical usage:
def typical_usage(code):
... try:
... code()
... except Exception, e:
... simplicity = lambda self: str(e) + , sorry!
... raise modify_message(e, simplicity)
Note that if we want to re-cycle the original exception's message,
then we need our re-formatter (here called 'simplicity') to be
defined inside the exception handler. I tried verious approaches
to defining the re-formater, but all of them eventually needed a
closure; I decided that I liked this approach best.
This harness wraps the example so that doctest doesn't get upset.
def test_harness(code):
... try:
... typical_usage(code)
... except Exception, e:
... print %s: %s % (e.__class__.__name__, str(e))
Now for some test cases:
test_harness(lambda: 1/0)
ZeroDivisionError: integer division or modulo by zero, sorry!
test_harness(lambda: unicode('\xe4'))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe4 in position
0: ordinal not in range(128), sorry!
def modify_message(old, f):
modify_message(exception, mutator) -- exception
Modifies the string representation of an exception.
class NewStyle(old.__class__):
def __init__(self): pass
NewStyle.__name__ = old.__class__.__name__
NewStyle.__str__ = f
new = NewStyle()
new.__dict__ = old.__dict__.copy()
return new
def _test():
import doctest
return doctest.testmod(verbose=True)
if __name__ == __main__:
_test()
--
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Re: Re-raising exceptions with modified message
On Jul 8, 8:50 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
Did you run this?
With Py 2.5 I get a syntax error, and with Py 2.5 I get:
new.__class__ = old.__class__
TypeError: __class__ must be set to a class
-- Chris
Damn, I'd have sworn I ran the final copy that I posted, but
apparently I did manage to have a typo creep in as I was prettifying
the code. You need to lose the '()' in the definition of Empty. (I'd
orignally had it subclass Exception but discovered that it wasn't
needed.)
class Empty: pass
I can't figure out the other complaint, though, as old.__class_ should
be a class. I guess I need to upgrade; I am using PythonWin 2.4.3
(#69, Apr 11 2006, 15:32:42) [MSC v.1310 32 bit (Intel)] on win32.
(Of course, at work they're still stuck on 2.4.2.) Printing
type(old.__class__) gives me type 'classobj'; maybe using
setattr(new, '__class__', old.__class__)
instead of the assignment would work, or maybe it's a bug/feature
introduced in 2.5. (Trying this code:
class Empty(old.__class__): pass
brings us back to the TypeError: function takes exactly 5 arguments
(0 given) message that we're trying to avoid.)
Anyway, running the corrected version under 2.4.X gives me this:
Traceback (most recent call last):
File C:\Python24\Lib\site-packages\pythonwin\pywin\framework
\scriptutils.py, line 310, in RunScript
exec codeObject in __main__.__dict__
File C:\Documents and Settings\dentos\Desktop\scripting
\modify_message.py, line 19, in ?
test(lambda: unicode('\xe4'))
File C:\Documents and Settings\dentos\Desktop\scripting
\modify_message.py, line 16, in test
raise modify_message(e, lambda: str(e) + , sorry!)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe4 in position
0: ordinal not in range(128), sorry!
--
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Re: Re-raising exceptions with modified message
On Jul 12, 6:31 am, samwyse [EMAIL PROTECTED] wrote: On Jul 8, 8:50 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: With Py 2.5 I get: new.__class__ = old.__class__ TypeError: __class__ must be set to a class Hmmm, under Python 2.4.X, printing repr(old.__class__) gives me this: class exceptions.UnicodeDecodeError at 0x00A24F00 while under 2.5.X, I get this: type 'exceptions.UnicodeDecodeError' So, let's try sub-classing the type: def modify_message(old, f): class Empty: pass new = Empty() print old.__class__ =, repr(old.__class__) print Empty =, repr(Empty) new.__class__ = Empty class Excpt(old.__class__): pass print Excpt =, repr(Excpt) print Excpt.__class__ =, repr(Excpt.__class__) new.__class__ = Excpt new.__dict__ = old.__dict__.copy() new.__str__ = f return new Nope, that gives us the same message: old.__class__ = type 'exceptions.UnicodeDecodeError' Empty = class __main__.Empty at 0x00AB0AB0 Excpt = class '__main__.Excpt' Excpt.__class__ = type 'type' Traceback (most recent call last): [...] TypeError: __class__ must be set to a class Excpt ceratinly appears to be a class. Does anyone smarter than me know what's going on here? -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
samwyse wrote: TypeError: __class__ must be set to a class Excpt ceratinly appears to be a class. Does anyone smarter than me know what's going on here? Not that I want to appear smarter, but I think the problem here is that exceptions are new-style classes now, whereas Empty is an old-style class. But even if you define Empty as a new-style class, it will not work, you get: TypeError: __class__ assignment: only for heap types This tells us that we cannot change the attributes of a built-in exception. If it would be possible, I simply would have overridden the __str__ method of the original exception in the first place. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Did you run this? With Py 2.5 I get a syntax error, and with Py 2.5 I get: new.__class__ = old.__class__ TypeError: __class__ must be set to a class -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
samwyse wrote: def test(code): try: code() except Exception, e: try: raise e.__class__, str(e) + , sorry! except TypeError: raise SorryFactory(e)() Ok, you're suggestig the naive approach if it works and the factory approach I came up with last as a fallback. Maybe a suitable compromize. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Gerard Flanagan wrote: Would a decorator work here? Depends on how you want to use that functionality. In my use case I only need to catch the excpetion once. Note that in your code the exception has not the right type which is what I targeted in my last posting. I.e. the following will raise an Exception if function is decorated: try: print funktion() except ArithmeticError: pass -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On Jul 5, 8:53 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)? Let's say for simplicity I just want to add sorry to every
exception message. My naive solution was this:
try:
...
except Exception, e:
raise e.__class__, str(e) + , sorry!
This works pretty well for most exceptions, e.g.
try:
... 1/0
... except Exception, e:
... raise e.__class__, str(e) + , sorry!
...
Traceback (most recent call last):
File stdin, line 4, in module
ZeroDivisionError: integer division or modulo by zero, sorry!
But it fails for some exceptions that cannot be instantiated with a
single string argument, like UnicodeDecodeError which gets converted
to a TypeError:
try:
... unicode('\xe4')
... except Exception, e:
... raise e.__class__, str(e) + , sorry!
...
Traceback (most recent call last):
File stdin, line 4, in module
TypeError: function takes exactly 5 arguments (1 given)
Another approach is using a wrapper Extension class:
class SorryEx(Exception):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
return str(self._e) + , sorry!
try:
unicode('\xe4')
except Exception, e:
raise SorryEx(e)
But then I get the name of the wrapper class in the message:
__main__.SorryEx: 'ascii' codec can't decode byte 0xe4 in position 0:
ordinal not in range(128), sorry!
Yet another approach would be to replace the __str__ method of e, but
this does not work for new style Exceptions (Python 2.5).
Any suggestions?
-- Chris
Can try statements be used in except clauses? It appears so, thus
a hybrid approach might work well enough.
try:
...
except Exception, e:
try:
raise e.__class__, str(e) + , sorry!
except TypeError:
raise SorryEx(e)
That leaves the issue of the name being changed for
UnicodeDecodeError, which might be fixable by diddling with __name__
properties. Or perhaps SorryEx needs to be a factory that returns
exception classes; the last line would be SorryEx(e)(). I'll have
to play with this a bit.
--
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Re: Re-raising exceptions with modified message
On Jul 7, 4:13 pm, samwyse [EMAIL PROTECTED] wrote:
On Jul 5, 8:53 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)?
[...]
That leaves the issue of the name being changed for
UnicodeDecodeError, which might be fixable by diddling with __name__
properties. Or perhaps SorryEx needs to be a factory that returns
exception classes; the last line would be SorryEx(e)(). I'll have
to play with this a bit.
OK, the following mostly works. You probably want the factory to copy
more of the original class into the SorryEx class each time, since
someone catching an exception may expect to look at things besides its
string representation.
def SorryFactory(e):
class SorryEx(Exception):
def __init__(self):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
return str(self._e) + , sorry!
SorryEx.__name__ = e.__class__.__name__
return SorryEx
def test(code):
try:
code()
except Exception, e:
try:
raise e.__class__, str(e) + , sorry!
except TypeError:
raise SorryFactory(e)()
test(lambda: unicode('\xe4'))
--
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Re: Re-raising exceptions with modified message
On Jul 5, 8:53 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)? Let's say for simplicity I just want to add sorry to every
exception message.
OK, this seems pretty minimal, yet versatile. It would be nice to be
able to patch the traceback, but it turns out that it's fairly hard to
do. If you really want to do that, however, go take a look at
http://lucumr.pocoo.org/cogitations/2007/06/16/patching-python-tracebacks-part-two/
# Written by Sam Denton [EMAIL PROTECTED]
# You may use, copy, or distribute this work,
# as long as you give credit to the original author.
def rewriten_exception(old, f):
class Empty(): pass
new = Empty()
new.__class__ = old.__class__
new.__dict__ = old.__dict__.copy()
new.__str__ = f
return new
def test(code):
try:
code()
except Exception, e:
raise rewriten_exception(e, lambda: str(e) + , sorry!)
test(lambda: unicode('\xe4'))
test(lambda: 1/0)
--
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Re: Re-raising exceptions with modified message
On Jul 6, 4:20 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Alex Popescu wrote: -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On Jul 6, 4:20 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Alex Popescu wrote: Probably the simplest solution would be to create a new exception and wrapping the old one and the additional info. Unfortunately, this may have a huge impact on 3rd party code that was catching the original exception. So, I think you should create an utility factory-like function that is either creating a new exception instance as the one caught and with the additional information, Right, I have gone with that (see the example with the PoliteException class somewhere below). or an utility that knows how to modify the caught exception according to its type. I guess you mean something like this (simplified): except Exception, e: if getattr(e, 'reason'): e.reason += sorry else: e.message += sorry The problem is that these attribute names are not standardized and can change between Python versions. Not even args is sure, and if a class has message it does not mean that it is displayed. Therefore I think the first approach is better. In the first case you will need somehow to tell to the new instance exception the real stack trace, because by simply raising a new one the original stack trace may get lost. Yes, but thats a different problem that is easy to solve. Yeah maybe for a python guy, but I am a newbie. I would really appreciate if you can show in this thread how this can be done in Python. tia, ./alex -- .w( the_mindstorm )p. PS: sorry for reposting, but it looks like my previous message hasn't gone through :-(. -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On 2007-07-06, Alex Popescu [EMAIL PROTECTED] wrote: On Jul 6, 4:20 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Alex Popescu wrote: Probably the simplest solution would be to create a new exception and wrapping the old one and the additional info. Unfortunately, this may have a huge impact on 3rd party code that was catching the original exception. So, I think you should create an utility factory-like function that is either creating a new exception instance as the one caught and with the additional information, Right, I have gone with that (see the example with the PoliteException class somewhere below). or an utility that knows how to modify the caught exception according to its type. I guess you mean something like this (simplified): except Exception, e: if getattr(e, 'reason'): e.reason += sorry else: e.message += sorry The problem is that these attribute names are not standardized and can change between Python versions. Not even args is sure, and if a class has message it does not mean that it is displayed. Therefore I think the first approach is better. In the first case you will need somehow to tell to the new instance exception the real stack trace, because by simply raising a new one the original stack trace may get lost. Yes, but thats a different problem that is easy to solve. Yeah maybe for a python guy, but I am a newbie. I would really appreciate if you can show in this thread how this can be done in Python. Chech out the docs for sys.exc_info(), and for the raise statement. When handling an exception, you can rethrow a different exception, but with the same traceback, by using the three-arg version of raise. See one of my earlier posts in this thread for a working example (although it didn't solve Chris's problem). -- Neil Cerutti -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On Jul 6, 12:18 am, Christoph Zwerschke [EMAIL PROTECTED] wrote:
Sorry for the soliloquy, but what I am really using is the following so
that the re-raised excpetion has the same type:
def PoliteException(e):
class PoliteException(e.__class__):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
if isinstance(self._e, PoliteException):
return str(self._e)
else:
return '\n%s: %s, I am sorry!' % (
self._e.__class__.__name__, str(self._e))
return PoliteException(e)
try:
unicode('\xe4')
except Exception, e:
raise PoliteException(e)
Would a decorator work here?
class PoliteException(Exception):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
return '\n%s: %s, I am sorry!' % (
self._e.__class__.__name__, str(self._e))
def politefail(fn):
def wrapper(*args, **kwargs):
try:
return fn(*args, **kwargs)
except Exception, e:
raise PoliteException(e)
return wrapper
@politefail
def funktion():
unicode('\xe4')
funktion()
@politefail
def raise_exception(err, *args):
raise err(*args)
def funktion():
if 1 != 2:
raise_exception(ArithmeticError, '1 is not equal to 2.')
print
funktion()
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Re: Re-raising exceptions with modified message
Christoph Zwerschke schrieb: What is the best way to re-raise any exception with a message supplemented with additional information (e.g. line number in a template)? I have the impression that you do NOT want to change the exceptions, instead you want to print the traceback in a customized way. But I may be wrong... Thomas -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Thomas Heller wrote: I have the impression that you do NOT want to change the exceptions, instead you want to print the traceback in a customized way. But I may be wrong... No, I really want to modify the exception, supplementing its message with additional information about the state of the program. The use case are compiled Kid templates (http://kid-templating.org). If an error occurs, I want to add the corresponding line number of the XML file as information for the template developer. Since the final error handling may happen somewhere else (e.g. by TurboGears importing a Kid template), I do not want to modify trackeback handling or something. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On 2007-07-05, Christoph Zwerschke [EMAIL PROTECTED] wrote: Thomas Heller wrote: I have the impression that you do NOT want to change the exceptions, instead you want to print the traceback in a customized way. But I may be wrong... No, I really want to modify the exception, supplementing its message with additional information about the state of the program. The use case are compiled Kid templates (http://kid-templating.org). If an error occurs, I want to add the corresponding line number of the XML file as information for the template developer. Since the final error handling may happen somewhere else (e.g. by TurboGears importing a Kid template), I do not want to modify trackeback handling or something. The documentation for BaseException contains something that might be relevant: [...] If more data needs to be attached to the exception, attach it through arbitrary attributes on the instance. All arguments are also stored in args as a tuple, but it will eventually be deprecated and thus its use is discouraged. New in version 2.5. [...] I don't know if something like the following would help: def foo(): ... try: ... 12/0 ... except ZeroDivisionError, e: ... e.my_info = Oops! ... raise ... try: ... foo() ... except ZeroDivisionError, e: ... print e.my_info ... Oops! Users could get at the extra info you attached, but it wouldn't be automatically displayed by the interpreter. -- Neil Cerutti Symphonies of the Romantic era were a lot longer in length. --Music Lit Essay -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Neil Cerutti wrote: The documentation for BaseException contains something that might be relevant: [...] If more data needs to be attached to the exception, attach it through arbitrary attributes on the instance. All Users could get at the extra info you attached, but it wouldn't be automatically displayed by the interpreter. Yes, that's the problem here. It wouldn't be displayed automatically and the users must be aware of this attribute. I'd like to have a more transparent solution. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
On 2007-07-05, Christoph Zwerschke [EMAIL PROTECTED] wrote:
Neil Cerutti wrote:
The documentation for BaseException contains something that might
be relevant:
[...] If more data needs to be attached to the exception,
attach it through arbitrary attributes on the instance. All
Users could get at the extra info you attached, but it wouldn't
be automatically displayed by the interpreter.
Yes, that's the problem here. It wouldn't be displayed
automatically and the users must be aware of this attribute.
I'd like to have a more transparent solution.
You ought to be able to use the third arg of raise to raise a new
exception as if it were from the previous location, but now with
a new message.
You may need the traceback module to get at the error message, if
trying to read e.message can fail.
Something like this mess here: ;)
...
except Exception, e:
etype, evalue, etb = sys.exc_info()
ex = traceback.format_exception_only(etype, evalue)
message = ex[0].partition(':')[2].strip()
raise etype, message+. Sorry!, etb
Note that the above will break for SyntaxError (who's message
contains more than one line) and any kind of exception that
doesn't inherit from Exception.
You might need some crufty try, finally to avoid having a
circular reference hang around, according to the docs for
sys.exc_info.
--
Neil Cerutti
--
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Re: Re-raising exceptions with modified message
Neil Cerutti wrote:
You may need the traceback module to get at the error message, if
trying to read e.message can fail.
Something like this mess here: ;)
...
except Exception, e:
etype, evalue, etb = sys.exc_info()
ex = traceback.format_exception_only(etype, evalue)
message = ex[0].partition(':')[2].strip()
raise etype, message+. Sorry!, etb
Note that the above will break for SyntaxError (who's message
contains more than one line) and any kind of exception that
doesn't inherit from Exception.
That's actually similar to what I was using in Kid already.
The problem is that there are some Exceptions which cannot be
instantiated with a single string argument, such as UnicodeDeocdeError.
Please try the above with unicode('\xe4') instead of the dots.
Instead of re-raising the UnicodeDecodeError, you will get a TypeError
because of this problem.
-- Chris
--
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Re: Re-raising exceptions with modified message
On 2007-07-05, Christoph Zwerschke [EMAIL PROTECTED] wrote:
Neil Cerutti wrote:
You may need the traceback module to get at the error message, if
trying to read e.message can fail.
Something like this mess here: ;)
...
except Exception, e:
etype, evalue, etb = sys.exc_info()
ex = traceback.format_exception_only(etype, evalue)
message = ex[0].partition(':')[2].strip()
raise etype, message+. Sorry!, etb
Note that the above will break for SyntaxError (who's message
contains more than one line) and any kind of exception that
doesn't inherit from Exception.
That's actually similar to what I was using in Kid already.
The problem is that there are some Exceptions which cannot be
instantiated with a single string argument, such as
UnicodeDeocdeError. Please try the above with unicode('\xe4')
instead of the dots. Instead of re-raising the
UnicodeDecodeError, you will get a TypeError because of this
problem.
Crud. After my third answer, I'll finally understand the
question. Unfortunately, I only had two in me.
--
Neil Cerutti
Low Self-Esteem Support Group will meet Thursday at 7 to 8:30 p.m. Please use
the back door. --Church Bulletin Blooper
--
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Re: Re-raising exceptions with modified message
On Jul 5, 3:53 pm, Christoph Zwerschke [EMAIL PROTECTED] wrote:
What is the best way to re-raise any exception with a message
supplemented with additional information (e.g. line number in a
template)? Let's say for simplicity I just want to add sorry to every
exception message. My naive solution was this:
try:
...
except Exception, e:
raise e.__class__, str(e) + , sorry!
This works pretty well for most exceptions, e.g.
try:
... 1/0
... except Exception, e:
... raise e.__class__, str(e) + , sorry!
...
Traceback (most recent call last):
File stdin, line 4, in module
ZeroDivisionError: integer division or modulo by zero, sorry!
But it fails for some exceptions that cannot be instantiated with a
single string argument, like UnicodeDecodeError which gets converted
to a TypeError:
try:
... unicode('\xe4')
... except Exception, e:
... raise e.__class__, str(e) + , sorry!
...
Traceback (most recent call last):
File stdin, line 4, in module
TypeError: function takes exactly 5 arguments (1 given)
Another approach is using a wrapper Extension class:
class SorryEx(Exception):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
return str(self._e) + , sorry!
try:
unicode('\xe4')
except Exception, e:
raise SorryEx(e)
But then I get the name of the wrapper class in the message:
__main__.SorryEx: 'ascii' codec can't decode byte 0xe4 in position 0:
ordinal not in range(128), sorry!
Yet another approach would be to replace the __str__ method of e, but
this does not work for new style Exceptions (Python 2.5).
Any suggestions?
-- Chris
If you are sure that the exception isn't caught on another level just
use the following showtraceback() function, manipulate it's output
slightly and terminate your program with sys.exit()
def showtraceback():
'''
(Copied from code.py)
'''
try:
type, value, tb = sys.exc_info()
sys.last_type = type
sys.last_value = value
sys.last_traceback = tb
tblist = traceback.extract_tb(tb)
del tblist[:1]
lst = traceback.format_list(tblist)
if lst:
lst.insert(0, Traceback (most recent call last):\n)
lst[len(lst):] = traceback.format_exception_only(type,
value)
finally:
tblist = tb = None
sys.stderr.write(.join(lst))
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Re: Re-raising exceptions with modified message
Kay Schluehr wrote: If you are sure that the exception isn't caught on another level just use the following showtraceback() function, manipulate it's output slightly and terminate your program with sys.exit() That's what I want to avoid. In my case the error is displayed and evaluated in a completly different piece of software. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Seems that no simple solution exists,
so for now, I will be using something like this:
class PoliteException(Exception):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
if isinstance(self._e, PoliteException):
return str(self._e)
else:
return '\n%s: %s, I am sorry!' % (
self._e.__class__.__name__, str(self._e))
try:
unicode('\xe4')
except Exception, e:
raise PoliteException(e)
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Re: Re-raising exceptions with modified message
On Jul 6, 12:21 am, Christoph Zwerschke [EMAIL PROTECTED] wrote: Kay Schluehr wrote: If you are sure that the exception isn't caught on another level just use the following showtraceback() function, manipulate it's output slightly and terminate your program with sys.exit() That's what I want to avoid. In my case the error is displayed and evaluated in a completly different piece of software. -- Chris Probably the simplest solution would be to create a new exception and wrapping the old one and the additional info. Unfortunately, this may have a huge impact on 3rd party code that was catching the original exception. So, I think you should create an utility factory-like function that is either creating a new exception instance as the one caught and with the additional information, or an utility that knows how to modify the caught exception according to its type. In the first case you will need somehow to tell to the new instance exception the real stack trace, because by simply raising a new one the original stack trace may get lost. bests, ./alex -- .w( the_mindstorm )p. -- http://mail.python.org/mailman/listinfo/python-list
Re: Re-raising exceptions with modified message
Sorry for the soliloquy, but what I am really using is the following so
that the re-raised excpetion has the same type:
def PoliteException(e):
class PoliteException(e.__class__):
def __init__(self, e):
self._e = e
def __getattr__(self, name):
return getattr(self._e, name)
def __str__(self):
if isinstance(self._e, PoliteException):
return str(self._e)
else:
return '\n%s: %s, I am sorry!' % (
self._e.__class__.__name__, str(self._e))
return PoliteException(e)
try:
unicode('\xe4')
except Exception, e:
raise PoliteException(e)
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Re: Re-raising exceptions with modified message
Alex Popescu wrote: Probably the simplest solution would be to create a new exception and wrapping the old one and the additional info. Unfortunately, this may have a huge impact on 3rd party code that was catching the original exception. So, I think you should create an utility factory-like function that is either creating a new exception instance as the one caught and with the additional information, Right, I have gone with that (see the example with the PoliteException class somewhere below). or an utility that knows how to modify the caught exception according to its type. I guess you mean something like this (simplified): except Exception, e: if getattr(e, 'reason'): e.reason += sorry else: e.message += sorry The problem is that these attribute names are not standardized and can change between Python versions. Not even args is sure, and if a class has message it does not mean that it is displayed. Therefore I think the first approach is better. In the first case you will need somehow to tell to the new instance exception the real stack trace, because by simply raising a new one the original stack trace may get lost. Yes, but thats a different problem that is easy to solve. -- Chris -- http://mail.python.org/mailman/listinfo/python-list
