Showing the method's class in expection's traceback

[Agustin Villena]

Hi!

is there anyway to show the class of a method in an exception's
traceback?

For example, the next code

class Some(object):
def foo(self,x):
raise Exception(x)

obj = Some()
obj.foo("some arg")

produces the next traceback

Traceback (most recent call last):
File "<string>", line 231, in run_nodebug
File "G:\dev\excepti ons\sample.py", line 7, in <module>
obj.foo("some arg")
File "G:\dev\excepti ons\sample.py", line 3, in foo
raise Exception(x)
Exception: some arg

I want to improve the line
File "G:\dev\excepti ons\sample.py", line 3, in foo

to
File "G:\dev\excepti ons\sample.py", line 3, in Some.foo

Is this improvement feasible

[Diez B. Roggisch]

Re: Showing the method's class in expection's traceback

Agustin Villena schrieb:

Hi!
>
is there anyway to show the class of a method in an exception's
traceback?
>
For example, the next code
>
class Some(object):
def foo(self,x):
raise Exception(x)
>
obj = Some()
obj.foo("some arg")
>
produces the next traceback
>
Traceback (most recent call last):
File "<string>", line 231, in run_nodebug
File "G:\dev\excepti ons\sample.py", line 7, in <module>
obj.foo("some arg")
File "G:\dev\excepti ons\sample.py", line 3, in foo
raise Exception(x)
Exception: some arg
>
I want to improve the line
File "G:\dev\excepti ons\sample.py", line 3, in foo
>
to
File "G:\dev\excepti ons\sample.py", line 3, in Some.foo
>
Is this improvement feasible

It should be. You can get a dictionary of the locals of an exception
stack frame, of which you could extract the self-parameter's class.

Diez

[Gabriel Genellina]

Re: Showing the method's class in expection's traceback

En Sun, 18 May 2008 17:31:44 -0300, Diez B. Roggisch <deets@nospam.w eb.deescribió:

Agustin Villena schrieb:

>is there anyway to show the class of a method in an exception's
>traceback?
>>
>I want to improve the line
>File "G:\dev\excepti ons\sample.py", line 3, in foo
>>
>to
>File "G:\dev\excepti ons\sample.py", line 3, in Some.foo
>>
>Is this improvement feasible

>
It should be. You can get a dictionary of the locals of an exception
stack frame, of which you could extract the self-parameter's class.

That by itself is not enough, the method could be inherited; one should walk the base classes in the MRO to find the right one. And deal with classmethods and staticmethods. And decorators that don't preserve meta information... Hmmm, I think it isn't so trivial as it seems.

--
Gabriel Genellina

[Diez B. Roggisch]

Re: Showing the method's class in expection's traceback

>

That by itself is not enough, the method could be inherited; one should
walk the base classes in the MRO to find the right one. And deal with
classmethods and staticmethods. And decorators that don't preserve meta
information... Hmmm, I think it isn't so trivial as it seems.

You might even have an instance-unique method. But I think the OP is
satisfied with a 90%-solution.

Diez

[Agustin Villena]

Re: Showing the method's class in expection's traceback

On May 18, 4:31 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Agustin Villena schrieb:
>
>
>

Hi!

>

is there anyway to show the class of amethodin an exception's
traceback?

>

For example, the next code

>

class Some(object):
def foo(self,x):
raise Exception(x)

>

obj = Some()
obj.foo("some arg")

>

produces the next traceback

>

Traceback (most recent call last):
File "<string>", line 231, in run_nodebug
File "G:\dev\excepti ons\sample.py", line 7, in <module>
obj.foo("some arg")
File "G:\dev\excepti ons\sample.py", line 3, in foo
raise Exception(x)
Exception: some arg

>

I want to improve the line
File "G:\dev\excepti ons\sample.py", line 3, in foo

>

to
File "G:\dev\excepti ons\sample.py", line 3, in Some.foo

>

Is this improvement feasible

>
It should be. You can get a dictionary of the locals of an exception
stack frame, of which you could extract the self-parameter's class.
>
Diez

Hi!

I digged on sys.exc_info() object and the traceback module and I
could't figure how I can get the locals() of the exception stackframe

Any advice?

Thanks
Agustin

[Gabriel Genellina]

Re: Showing the method's class in expection's traceback

En Mon, 19 May 2008 10:54:05 -0300, Agustin Villena
<agustin.villen a@gmail.comescr ibió:

On May 18, 4:31 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

>Agustin Villena schrieb:
>>

is there anyway to show the class of amethodin an exception's
traceback?
I want to improve the line
File "G:\dev\excepti ons\sample.py", line 3, in foo
to
File "G:\dev\excepti ons\sample.py", line 3, in Some.foo

>>
>It should be. You can get a dictionary of the locals of an exception
>stack frame, of which you could extract the self-parameter's class.

>
I digged on sys.exc_info() object and the traceback module and I
could't figure how I can get the locals() of the exception stackframe

Put this function in traceback.py, and replace the lines
name = co.co_name
with
name = guess_full_meth od_name(f)
everywhere.
Please read the docstring!!!

def guess_full_meth od_name(frame):
"""Guess classname.metho dname for a given frame.

Only a guess!
Assumes the frame belongs to an instancemethod
whose first argument is "self", or a classmethod
whose first argument is "cls".
Doesn't handle correctly any other situation.
Returns the class name of the object on which
the method was called, not the class where
the method was actually defined.
"""
cls_name = None
fun_name = frame.f_code.co _name
self = frame.f_locals. get('self', None)
if self is None:
cls = frame.f_locals. get('cls', None)
else:
cls = getattr(self, '__class__', None)
if cls is not None:
cls_name = getattr(cls, '__name__', None)
if cls_name is not None:
return '%s.%s' % (cls_name, fun_name)
return fun_name

--
Gabriel Genellina

[Bruno Desthuilliers]

Re: Showing the method's class in expection's traceback

Gabriel Genellina a écrit :

En Sun, 18 May 2008 17:31:44 -0300, Diez B. Roggisch
<deets@nospam.w eb.deescribió:

>Agustin Villena schrieb:

>

>>is there anyway to show the class of a method in an exception's
>>traceback?
>>>
>>I want to improve the line File "G:\dev\excepti ons\sample.py",
>>line 3, in foo
>>>
>>to File "G:\dev\excepti ons\sample.py", line 3, in Some.foo
>>>
>>Is this improvement feasible

>It should be. You can get a dictionary of the locals of an
>exception stack frame, of which you could extract the
>self-parameter's class.

>
That by itself is not enough, the method could be inherited; one
should walk the base classes in the MRO to find the right one. And
deal with classmethods and staticmethods. And decorators that don't
preserve meta information...

And monkeypatches.

Hmmm, I think it isn't so trivial as it
seems.

And not that useful - why would one care about the function being
defined in class X or Y when one have the exact file and line ?

[Richard G Riley]

Re: Showing the method's class in expection's traceback

Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:

Gabriel Genellina a écrit :

>En Sun, 18 May 2008 17:31:44 -0300, Diez B. Roggisch
><deets@nospam. web.deescribió :

>>Agustin Villena schrieb:

>>

>>>is there anyway to show the class of a method in an exception's
>>>traceback?
>>>>
>>>I want to improve the line File "G:\dev\excepti ons\sample.py",
>>>line 3, in foo
>>>>
>>>to File "G:\dev\excepti ons\sample.py", line 3, in Some.foo
>>>>
>>>Is this improvement feasible
>>It should be. You can get a dictionary of the locals of an
>>exception stack frame, of which you could extract the
>>self-parameter's class.

>>
>That by itself is not enough, the method could be inherited; one
>should walk the base classes in the MRO to find the right one. And
>deal with classmethods and staticmethods. And decorators that don't
>preserve meta information...

>
And monkeypatches.
>

>Hmmm, I think it isn't so trivial as it
>seems.

>
And not that useful - why would one care about the function being
defined in class X or Y when one have the exact file and line ?

Very obvious I would think. One can develop ones own interactive class
browser and code navigator. One can not bring up class help from "line 3
in x.py" but one can from "classname : MyClass at line 2 in z.py". With
the class name I can navigate directly to all sorts of class related
information without the need to delve into a physical usage of it e.g
program.py at line 3.

[Bruno Desthuilliers]

Re: Showing the method's class in expection's traceback

Richard G Riley a écrit :

Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:

(snip)

>And not that useful - why would one care about the function being
>defined in class X or Y when one have the exact file and line ?

>
Very obvious I would think. One can develop ones own interactive class
browser and code navigator.

From the traceback ?

One can not bring up class help from "line 3
in x.py" but one can from "classname : MyClass at line 2 in z.py". With
the class name I can navigate directly to all sorts of class related
information without the need to delve into a physical usage of it e.g
program.py at line 3.

Please bear with me, but I'm afraid I still don't get the point : I
don't need tracebacks to get to some object's info (help etc).

[Richard G Riley]

Re: Showing the method's class in expection's traceback

Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:

Richard G Riley a écrit :

>Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:

>
(snip)
>

>>And not that useful - why would one care about the function being
>>defined in class X or Y when one have the exact file and line ?

>>
>Very obvious I would think. One can develop ones own interactive class
>browser and code navigator.

>
From the traceback ?
>

> One can not bring up class help from "line 3
>in x.py" but one can from "classname : MyClass at line 2 in z.py". With
>the class name I can navigate directly to all sorts of class related
>information without the need to delve into a physical usage of it e.g
>program.py at line 3.

>
Please bear with me, but I'm afraid I still don't get the point : I
don't need tracebacks to get to some object's info (help etc).

This is a view quite common to people when they are happy with what they
have. Some like to improve what they have. It is immediately apparent to
me why having a class name and method name in the traceback would be
immediately useful. Having written a few extensions to IDEs in the past
I know it would help me, and I suspect, the original poster. As a recent
"recruit" to Python I am quite surprised as how poor most of the query
like tools in the python shell are. The first thing I did was to move to
iPython. Still, horses for courses.

[Bruno Desthuilliers]

Re: Showing the method's class in expection's traceback

Richard G Riley a écrit :

Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:
>

>Richard G Riley a écrit :

>>Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ites:

>(snip)
>>

>>>And not that useful - why would one care about the function being
>>>defined in class X or Y when one have the exact file and line ?
>>Very obvious I would think. One can develop ones own interactive class
>>browser and code navigator.

>From the traceback ?
>>

>> One can not bring up class help from "line 3
>>in x.py" but one can from "classname : MyClass at line 2 in z.py". With
>>the class name I can navigate directly to all sorts of class related
>>information without the need to delve into a physical usage of it e.g
>>program.py at line 3.

>Please bear with me, but I'm afraid I still don't get the point : I
>don't need tracebacks to get to some object's info (help etc).

>
This is a view quite common to people when they are happy with what they
have. Some like to improve what they have. It is immediately apparent to
me why having a class name and method name in the traceback would be
immediately useful.

Then please explain.

Having written a few extensions to IDEs in the past
I know it would help me,

To do what ?

[Agustin Villena]

Re: Showing the method's class in expection's traceback

And not that useful - why would one care about the function being
defined in class X or Y when one have the exact file and line ?

I have 3 reasons:

1) My developing time is expended running unit tests and browsing
tracebacks to find which is the real problem. Knowing the offender
class (instead of the method alone) makes me understand more quickly
which component of my software is failing.
2) There are some ocassions where I only have the traceback (e.g. when
analyzing an app's log) and no inmediate access to teh source code
3) And finally, for completeness: If a function is really a method, if
the traceback show only its name and not the class that defines it,
for me its a bug, because the method name has no sense out of its
class.

Just my two cents

Agustin

[Agustin Villena]

Re: Showing the method's class in expection's traceback

On 20 mayo, 12:10, "Gabriel Genellina" <gagsl-...@yahoo.com.a rwrote:

En Mon, 19 May 2008 10:54:05 -0300, Agustin Villena
<agustin.vill.. .@gmail.comescr ibió:
>

On May 18, 4:31 pm, "Diez B. Roggisch" <de...@nospam.w eb.dewrote:

Agustin Villena schrieb:

>

is there anyway to show the class of amethodin anexception's
traceback?
I want to improve the line
File "G:\dev\excepti ons\sample.py", line 3, in foo
to
File "G:\dev\excepti ons\sample.py", line 3, in Some.foo

>

It should be. You can get a dictionary of the locals of anexception
stack frame, of which you could extract the self-parameter's class.

>

I digged on sys.exc_info() object and the traceback module and I
could't figure how I can get the locals() of theexceptionsta ckframe

>
Put this function in traceback.py, and replace the lines
name = co.co_name
with
name = guess_full_meth od_name(f)
everywhere.
Please read the docstring!!!
>
def guess_full_meth od_name(frame):
"""Guess classname.metho dname for a given frame.
>
Only a guess!
Assumes the frame belongs to an instancemethod
whose first argument is "self", or a classmethod
whose first argument is "cls".
Doesn't handle correctly any other situation.
Returns the class name of the object on which
the method was called, not the class where
the method was actually defined.
"""
cls_name = None
fun_name = frame.f_code.co _name
self = frame.f_locals. get('self', None)
if self is None:
cls = frame.f_locals. get('cls', None)
else:
cls = getattr(self, '__class__', None)
if cls is not None:
cls_name = getattr(cls, '__name__', None)
if cls_name is not None:
return '%s.%s' % (cls_name, fun_name)
return fun_name
>
--
Gabriel Genellina

Thanks! I'll try it

Agustin

[Bruno Desthuilliers]

Re: Showing the method's class in expection's traceback

Agustin Villena a écrit :

>And not that useful - why would one care about the function being
>defined in class X or Y when one have the exact file and line ?

>
I have 3 reasons:
>
1) My developing time is expended running unit tests and browsing
tracebacks to find which is the real problem. Knowing the offender
class (instead of the method alone) makes me understand more quickly
which component of my software is failing.

This is only true when there is an obvious, one-to-one, unambiguous
relationship between the physical location of the error (file, line) and
the class of the object the method has been called on. Which is not
necessarily the case (inheritance, method decoration and monkeypatching
comes to mind here...).

Also, your above statement seems to imply that component==clas s, which
is not the case in Python.

2) There are some ocassions where I only have the traceback (e.g. when
analyzing an app's log) and no inmediate access to teh source code

Ok. But the above still apply...

3) And finally, for completeness: If a function is really a method, if
the traceback show only its name and not the class that defines it,
for me its a bug, because the method name has no sense out of its
class.

I'm not sure you really grasp what "methods" are in Python. What you
define (using the def statement) within a class is function, not a
method. It only becomes a method when it's looked up on an instance or
class object, and this 'method' is only a thin wrapper around the
instance, class and function objects. And FWIW, you don't need to define
the function within the class to make it a method:

# bar.py
def bar(obj):
print "function bar.bar called on obj %s" % obj


# foo.py

class Foo(object): pass

# baaz.py
from foo import Foo
import bar

Foo.baaz = bar.bar

def guux(obj):
print "function baaz.guux called on obj %s" % obj

# main.py
from baaz import Foo
f = Foo()
f.bar()

f.gnix = baae.guux.__get __(f, type(f))
f.gnix()



Not to say that your concerns are pointless, and that things cannot be
improved somehow, but this is not that trivial, and there may be
ambuiguities in some not so rare cases.

[Duncan Booth]

Re: Showing the method's class in expection's traceback

Bruno Desthuilliers <bruno.42.desth uilliers@websit eburo.invalidwr ote:

Not to say that your concerns are pointless, and that things cannot be
improved somehow, but this is not that trivial, and there may be
ambuiguities in some not so rare cases.

It might be worth considering an alternative approach here: a formatted
exception includes the relevant source lines (where possible).

The source lines are cached by the module linecache.py and it probably
wouldn't be too hard to build on the line cache so that it also scans the
source lines looking for class statements and recording the start and end
line numbers for each class.

That way any classname displayed would be based on the actual source
nesting and even static methods or functions injected from another class
would work 'correctly' (at some level).

--
Duncan Booth http://kupuguy.blogspot.com