exceptions

[Zunbeltz Izaola]

Hi,

I've the following problem with try/exception.
I've a try block that will raise some exceptions.
I want the program to ignore this exceptions completely.
Is it possible?

Thanks in advance

Zunbeltz

--
Zunbeltz Izaola Azkona | wmbizazz at lg dot ehu
dotes
Materia Kondentsatuaren Fisika Saila |
Zientzia eta Teknologia Fakultatea | Phone: 34946015326
Euskal Herriko Unibertsitatea |
PK 644 | Fax: 34 944648500
48080 Bilbo (SPAIN) |

[Peter Hansen]

Re: exceptions

Zunbeltz Izaola wrote:[color=blue]
> I've the following problem with try/exception.
> I've a try block that will raise some exceptions.
> I want the program to ignore this exceptions completely.
> Is it possible?[/color]

In the following, all exceptions will be ignored:

try:
# something that raises exceptions
except:
pass

This is definitely *not* a recommended way to write software,
however. You should really understand what you are doing before
writing code this way.

-Peter

[Brian Gough]

Re: exceptions

Zunbeltz Izaola <zunbeltz@wm.lc .ehu.es.XXX> writes:
[color=blue]
> I've the following problem with try/exception.
> I've a try block that will raise some exceptions.
> I want the program to ignore this exceptions completely.
> Is it possible?[/color]

You can use an empty "except:" to catch all exceptions and ignore them,

try:
# your code
except:
pass

See the Python tutorial or language reference manual for details.

--
Brian Gough

Network Theory Ltd,
Publishing the Python Manuals --- http://www.network-theory.co.uk/

[Zunbeltz Izaola]

Re: exceptions

Peter Hansen <peter@engcorp. com> writes:
[color=blue]
> Zunbeltz Izaola wrote:[color=green]
> > I've the following problem with try/exception.
> > I've a try block that will raise some exceptions.
> > I want the program to ignore this exceptions completely. Is it
> > possible?[/color]
>
> In the following, all exceptions will be ignored:
>
> try:
> # something that raises exceptions
> except:
> pass
>[/color]

I've trid this, but the problem is that this finished the try block.
I want to continue executing the try block from the point the
exception was raised.
[color=blue]
> This is definitely *not* a recommended way to write software,
> however. You should really understand what you are doing before
> writing code this way.
>[/color]

I know. I need this feature for testing. I will desable it later.

Zunbeltz
[color=blue]
> -Peter[/color]

--
Zunbeltz Izaola Azkona | wmbizazz at lg dot ehu
dotes
Materia Kondentsatuaren Fisika Saila |
Zientzia eta Teknologia Fakultatea | Phone: 34946015326
Euskal Herriko Unibertsitatea |
PK 644 | Fax: 34 944648500
48080 Bilbo (SPAIN) |

[Jeff Epler]

Re: exceptions

Use "pass" as the body of the "except:" block. For example:

def put(s, i, j):
"""Store j at s[i], or do nothing if s is not that long"""
try:
s[i] = j
except IndexError:
pass
[color=blue][color=green][color=darkred]
>>> l = [1, 2, 3]
>>> put(l, 1, "hi")
>>> put(l, 4, "bye")
>>> l[/color][/color][/color]
[1, 'hi', 3]

Jeff

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[Peter Hansen]

Re: exceptions

Zunbeltz Izaola wrote:[color=blue]
> Peter Hansen <peter@engcorp. com> writes:[color=green]
>>Zunbeltz Izaola wrote:
>>[color=darkred]
>>>I've the following problem with try/exception.
>>>I've a try block that will raise some exceptions.
>>>I want the program to ignore this exceptions completely. Is it
>>>possible?[/color]
>>
>>In the following, all exceptions will be ignored:
>>
>>try:
>> # something that raises exceptions
>>except:
>> pass[/color]
>
> I've trid this, but the problem is that this finished the try block.
> I want to continue executing the try block from the point the
> exception was raised.[/color]

Not possible except, perhaps, with a significant amount of
working involving sys.settrace(). I think you need to find
another way to solve the problem.

What you are trying to do is not something that other people
who do unit testing seem to have to do. Why do you think
you need to actually *disable* exceptions entirely in order
to test this code? Perhaps the code needs to be restructured?

-Peter

[Zunbeltz Izaola]

Re: exceptions

Peter Hansen <peter@engcorp. com> writes:
[color=blue]
> Zunbeltz Izaola wrote:[color=green]
> > Peter Hansen <peter@engcorp. com> writes:[color=darkred]
> >>Zunbeltz Izaola wrote:
> >>
> >>>I've the following problem with try/exception.
> >>>I've a try block that will raise some exceptions.
> >>>I want the program to ignore this exceptions completely. Is it
> >>>possible?
> >>
> >>In the following, all exceptions will be ignored:
> >>
> >>try:
> >> # something that raises exceptions
> >>except:
> >> pass[/color]
> > I've trid this, but the problem is that this finished the try block.
> > I want to continue executing the try block from the point the
> > exception was raised.[/color]
>
> Not possible except, perhaps, with a significant amount of
> working involving sys.settrace(). I think you need to find
> another way to solve the problem.
>
> What you are trying to do is not something that other people
> who do unit testing seem to have to do. Why do you think
> you need to actually *disable* exceptions entirely in order
> to test this code? Perhaps the code needs to be restructured?[/color]

Possibly the code should be restructered, and re-designed; there is
always room for imporovement. But what I'm doing is not unittest. My
program is controling and instrument (an x-ray powder
diffractometer) and some parts of the instrument are not working for
the moment, so i want to disable all error i get from this instrument
(are coded like exceptions)

Zunbeltz[color=blue]
>
> -Peter[/color]

--
Zunbeltz Izaola Azkona | wmbizazz at lg dot ehu
dotes
Materia Kondentsatuaren Fisika Saila |
Zientzia eta Teknologia Fakultatea | Phone: 34946015326
Euskal Herriko Unibertsitatea |
PK 644 | Fax: 34 944648500
48080 Bilbo (SPAIN) |

[Irmen de Jong]

Re: exceptions

Zunbeltz Izaola wrote:
[color=blue]
> Possibly the code should be restructered, and re-designed; there is
> always room for imporovement. But what I'm doing is not unittest. My
> program is controling and instrument (an x-ray powder
> diffractometer) and some parts of the instrument are not working for
> the moment, so i want to disable all error i get from this instrument
> (are coded like exceptions)[/color]

What I usually do in comparable situations is to write STUB code for
the parts of the system that don't work yet.
Write your stub code so that it does nothing, but doesn't raise any
exceptions too. The only thing you then have to do is write the rest
of the code as you would have done, and once the Stubbed parts work,
replace the stub code with the real code.

--Irmen

[Calvin Spealman]

Re: exceptions

Peter Hansen wrote:[color=blue]
> Zunbeltz Izaola wrote:[color=green]
>> I've trid this, but the problem is that this finished the try block.
>> I want to continue executing the try block from the point the
>> exception was raised.[/color]
>
> Not possible except, perhaps, with a significant amount of
> working involving sys.settrace(). I think you need to find
> another way to solve the problem.[/color]

Have to admit tho, a continue feature might be useful. Some languages have
this, don't they? The thing is, Where exactly to continue? Should you retry
whatever raised the exception, continue just after it, at the beginning of
that line, or what?

[Scott David Daniels]

Re: exceptions

Calvin Spealman wrote:[color=blue]
> ...
> Have to admit tho, a continue feature might be useful. Some languages have
> this, don't they? The thing is, Where exactly to continue? Should you retry
> whatever raised the exception, continue just after it, at the beginning of
> that line, or what?
>
>[/color]
See this older thread:
<http://groups.google.c om/groups?threadm= 3edd6118%241%40 nntp0.pdx.net>

Xerox's experience (in deliberately removing the "continue from
exception" language feature) I found very instructive.

-Scott David Daniels
Scott.Daniels@A cm.Org

[John J. Lee]

Re: exceptions

Irmen de Jong <irmen@-nospam-remove-this-xs4all.nl> writes:
[color=blue]
> Zunbeltz Izaola wrote:
>[color=green]
> > Possibly the code should be restructered, and re-designed; there is
> > always room for imporovement. But what I'm doing is not unittest. My
> > program is controling and instrument (an x-ray powder
> > diffractometer) and some parts of the instrument are not working for
> > the moment, so i want to disable all error i get from this instrument
> > (are coded like exceptions)[/color]
>
> What I usually do in comparable situations is to write STUB code for
> the parts of the system that don't work yet.
> Write your stub code so that it does nothing, but doesn't raise any
> exceptions too. The only thing you then have to do is write the rest
> of the code as you would have done, and once the Stubbed parts work,
> replace the stub code with the real code.[/color]

....and if you think you want to get exceptions later:

def fixme():
pass


Sprinkle fixme()s through your code, then redefine later:

def fixme():
raise NotImplementedE rror()


John

[Peter Hansen]

Re: exceptions

Zunbeltz Izaola wrote:
[color=blue]
> Peter Hansen <peter@engcorp. com> writes:[color=green]
>>Zunbeltz Izaola wrote:[color=darkred]
>>>I want to continue executing the try block from the point the
>>>exception was raised.[/color]
>>
>>Not possible except, perhaps, with a significant amount of
>>working involving sys.settrace(). I think you need to find
>>another way to solve the problem.[/color]
>
> But what I'm doing is not unittest.[/color]

Pardon: I don't know why I thought this was related to testing
code.
[color=blue]
> My program is controling and instrument (an x-ray powder
> diffractometer) and some parts of the instrument are not working for
> the moment, so i want to disable all error i get from this instrument
> (are coded like exceptions)[/color]

What is the interface to the instrument? Is there some sort of
driver/wrapper layer that handles the communication with the
device? Your only hope, I think, is to intercept things at
that level and avoid/trap the exceptions before they get up
to the higher level. In effect, stubs as Irmen suggested...

It sounds like you are quite capable of figuring it out at
this point, though, since all you wanted to know was whether
you could continue after an exception and now you know you
cannot. :-)

-Peter

[Ng Pheng Siong]

Re: exceptions

According to Scott David Daniels <Scott.Daniels@ Acm.Org>:[color=blue]
> Calvin Spealman wrote:[color=green]
> > ...
> > Have to admit tho, a continue feature might be useful. Some languages have
> > this, don't they? The thing is, Where exactly to continue? Should you retry
> > whatever raised the exception, continue just after it, at the beginning of
> > that line, or what?
> >[/color]
> See this older thread:
> <http://groups.google.c om/groups?threadm= 3edd6118%241%40 nntp0.pdx.net>
>
> Xerox's experience (in deliberately removing the "continue from
> exception" language feature) I found very instructive.[/color]

Are the bugs mainly in the implementation of that feature, or in user
code attempting to use said feature?

(I notice the older thread was one year ago. Is this an annual topic? ;-)

BTW, Common Lisp has this, called "restarts". There are about half a dozen
Common Lisp implementations and none appear to have gotten restarts
terribly wrong.

Cheers.


--
Ng Pheng Siong <ngps@netmemeti c.com>

http://firewall.rulemaker.net -+- Firewall Change Management & Version Control
http://sandbox.rulemaker.net/ngps -+- ZServerSSL/Zope Windows Installers

[Jeff Epler]

Re: exceptions

> According to Scott David Daniels <Scott.Daniels@ Acm.Org>:[color=blue][color=green]
> > See this older thread:
> > <http://groups.google.c om/groups?threadm= 3edd6118%241%40 nntp0.pdx.net>[/color][/color]

On Tue, Jun 01, 2004 at 12:59:29AM +0000, Ng Pheng Siong wrote:[color=blue]
> (I notice the older thread was one year ago. Is this an annual topic? ;-)[/color]

Perhaps the older thread had an exception, but now it's been re-started?

Jeff

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[Jacek Generowicz]

Re: exceptions

Scott David Daniels <Scott.Daniels@ Acm.Org> writes:
[color=blue]
> Calvin Spealman wrote:[color=green]
> > ...
> > Have to admit tho, a continue feature might be useful. Some languages have
> > this, don't they? The thing is, Where exactly to continue? Should you retry
> > whatever raised the exception, continue just after it, at the beginning of
> > that line, or what?
> >[/color]
>
> See this older thread:
> <http://groups.google.c om/groups?threadm= 3edd6118%241%40 nntp0.pdx.net>
>
> Xerox's experience (in deliberately removing the "continue from
> exception" language feature) I found very instructive.[/color]

Funny, Common Lisp (and some of its ancestors) allows you to "fiddle
things and and return as well as even return from the exception", and
people who write industrial strength applications is Common Lisp
repeatedly state that this feature allows them to write software which
is much more robust than any they would otherwise be able to
create. Some go as far as considering any language without this
feature to be fundamentally flawed. I have never heard anyone identify
this feature as a source of bugs.

So I am tempted to conclude that the Mesa implementation was flawed
.... or maybe it was just the users who were flawed. The concept itself
seems to have proven its worth over time.