Re: Is there a way to continue after an exception ?
On 21-02-2010 03:51, Ryan Kelly wrote:
On Sun, 2010-02-21 at 13:17 +1100, Lie Ryan wrote:
On 02/21/10 12:02, Stef Mientki wrote:
On 21-02-2010 01:21, Lie Ryan wrote:
On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki
stef.mien...@gmail.com wrote:
hello,
I would like my program to continue on the next line after an uncaught
exception,
is that possible ?
thanks
Stef Mientki
That reminds me of VB's On Error Resume Next
I think that's what I'm after ...
A much better approach is to use callbacks, the callbacks determines
whether to raise an exception or continue execution:
def handler(e):
if datetime.datetime.now()= datetime.datetime(2012, 12, 21):
raise Exception('The world has ended')
# else: ignore, it's fine
def add_ten_error_if_zero(args, handler):
if args == 0:
handler(args)
return args + 10
print add_ten_error_if_zero(0, handler)
print add_ten_error_if_zero(10, handler)
print add_ten_error_if_zero(0, lambda e: None) # always succeeds
Or if you don't like having to explicitly manage callbacks, you can try
the withrestart module:
http://pypi.python.org/pypi/withrestart/
It tries to pinch some of the good ideas from Common Lisp's
error-handling system.
from withrestart import *
def add_ten_error_if_zero(n):
# This gives calling code the option to ignore
# the error, or raise a different one.
with restarts(skip,raise_error):
if n == 0:
raise ValueError
return n + 10
# This will raise ValueError
print add_ten_error_if_zero(0)
# This will print 10
with Handler(ValueError,skip):
print add_ten_error_if_zero(0)
# This will exit the python interpreter
with Handler(ValueError,raise_error,SystemExit):
print add_ten_error_if_zero(0)
Cheers,
Ryan
thanks Ryan (and others),
your description of withstart was very informative,
and I think I understand why it's impossible what I want
(something like madExcept for Delphi / C / C++, see
*http://www.madshi.net/madExceptDescription.htm )
*
It are not the bugs that you can predict / expect to catch,
but the uncaught bugs.
So made some first steps,
and this seems to be sufficient for now,
if you're interested, look here,
http://mientki.ruhosting.nl/data_www/pylab_works/pw_bug_reporter.html
cheers,
Stef
--
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Is there a way to continue after an exception ?
hello, I would like my program to continue on the next line after an uncaught exception, is that possible ? thanks Stef Mientki -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a way to continue after an exception ?
On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki stef.mien...@gmail.com wrote: hello, I would like my program to continue on the next line after an uncaught exception, is that possible ? thanks Stef Mientki Yes, you catch the exception and do nothing. -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a way to continue after an exception ?
On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki stef.mien...@gmail.com wrote: hello, I would like my program to continue on the next line after an uncaught exception, is that possible ? thanks Stef Mientki That reminds me of VB's On Error Resume Next -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a way to continue after an exception ?
On 02/21/10 12:02, Stef Mientki wrote:
On 21-02-2010 01:21, Lie Ryan wrote:
On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki
stef.mien...@gmail.com wrote:
hello,
I would like my program to continue on the next line after an uncaught
exception,
is that possible ?
thanks
Stef Mientki
That reminds me of VB's On Error Resume Next
I think that's what I'm after ...
First, read this:
http://www.developerfusion.com/code/4325/on-error-resume-next-considered-harmful/
I already redirected sys.excepthook to my own function,
but now I need a way to get to continue the code on the next line.
Is that possible ?
No, not in python. You can (ab)use generators' yield to resume
execution, but not in the general case:
def on_error_resume_next(func):
def _func(*args, **kwargs):
gen = func(*args, **kwargs)
resp = next(gen)
while isinstance(resp, Exception):
print 'an error happened, ignoring...'
resp = next(gen)
return resp
return _func
@on_error_resume_next
def add_ten_error_if_zero(args):
if args == 0:
# raise Exception()
yield Exception()
# return args + 10
yield args + 10
print add_ten_error_if_zero(0)
print add_ten_error_if_zero(10)
A slightly better approach is to retry calling the function again, but
as you can see, it's not appropriate for certain cases:
def retry_on_error(func):
def _func(*args, **kwargs):
while True:
try:
ret = func(*args, **kwargs)
except Exception:
print 'An error happened, retrying...'
else:
return ret
return _func
@retry_on_error
def add_ten_error_if_zero(args):
if args == 0:
raise Exception()
return args + 10
print add_ten_error_if_zero(0)
print add_ten_error_if_zero(10)
A much better approach is to use callbacks, the callbacks determines
whether to raise an exception or continue execution:
def handler(e):
if datetime.datetime.now() = datetime.datetime(2012, 12, 21):
raise Exception('The world has ended')
# else: ignore, it's fine
def add_ten_error_if_zero(args, handler):
if args == 0:
handler(args)
return args + 10
print add_ten_error_if_zero(0, handler)
print add_ten_error_if_zero(10, handler)
print add_ten_error_if_zero(0, lambda e: None) # always succeeds
Ignoring arbitrary error is against the The Zen of Python Errors should
never pass silently.; not that it is ever a good idea to ignore
arbitrary error, when an exception happens often the function is in an
indeterminate state, and continuing blindly could easily cause havocs.
--
http://mail.python.org/mailman/listinfo/python-list
Re: Is there a way to continue after an exception ?
On Feb 20, 2010, at 9:17 PM, Lie Ryan wrote: On 02/21/10 12:02, Stef Mientki wrote: On 21-02-2010 01:21, Lie Ryan wrote: On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki stef.mien...@gmail.com wrote: hello, I would like my program to continue on the next line after an uncaught exception, is that possible ? thanks Stef Mientki That reminds me of VB's On Error Resume Next I think that's what I'm after ... First, read this: http://www.developerfusion.com/code/4325/on-error-resume-next-considered-harmful/ The link goes to an Oh dear. Gremlins at work! page. They're probably using On Error Resume Next in their VBScript code and this is the last resort page ;-). S -- http://mail.python.org/mailman/listinfo/python-list
Re: Is there a way to continue after an exception ?
On Sun, 2010-02-21 at 13:17 +1100, Lie Ryan wrote:
On 02/21/10 12:02, Stef Mientki wrote:
On 21-02-2010 01:21, Lie Ryan wrote:
On Sun, Feb 21, 2010 at 12:52 AM, Stef Mientki
stef.mien...@gmail.com wrote:
hello,
I would like my program to continue on the next line after an uncaught
exception,
is that possible ?
thanks
Stef Mientki
That reminds me of VB's On Error Resume Next
I think that's what I'm after ...
A much better approach is to use callbacks, the callbacks determines
whether to raise an exception or continue execution:
def handler(e):
if datetime.datetime.now() = datetime.datetime(2012, 12, 21):
raise Exception('The world has ended')
# else: ignore, it's fine
def add_ten_error_if_zero(args, handler):
if args == 0:
handler(args)
return args + 10
print add_ten_error_if_zero(0, handler)
print add_ten_error_if_zero(10, handler)
print add_ten_error_if_zero(0, lambda e: None) # always succeeds
Or if you don't like having to explicitly manage callbacks, you can try
the withrestart module:
http://pypi.python.org/pypi/withrestart/
It tries to pinch some of the good ideas from Common Lisp's
error-handling system.
from withrestart import *
def add_ten_error_if_zero(n):
# This gives calling code the option to ignore
# the error, or raise a different one.
with restarts(skip,raise_error):
if n == 0:
raise ValueError
return n + 10
# This will raise ValueError
print add_ten_error_if_zero(0)
# This will print 10
with Handler(ValueError,skip):
print add_ten_error_if_zero(0)
# This will exit the python interpreter
with Handler(ValueError,raise_error,SystemExit):
print add_ten_error_if_zero(0)
Cheers,
Ryan
--
Ryan Kelly
http://www.rfk.id.au | This message is digitally signed. Please visit
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