Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Maric Michaud wrote: > Le Vendredi 09 Juin 2006 20:06, Ilias Lazaridis a écrit : >> the code below works, but has the limitation that I cannot import the >> syncdb_hook within "django.core.management". > > In [4]: from b import CONS > > In [5]: import b > > In [6]: b.CONS = 3 > > In [7]: CONS > Out[7]: 5 > > In [8]: from b import CONS > > In [9]: CONS > Out[9]: 3 > > So, if you change one module name, a function or a class or a constant, you > must do it before it is imported, or you must reload modules using it. But > either are not always possible, and the later is not what you want to achieve > here as it will re-execute all initialisation code in those modules. > > But think of that, a function is hopefully an object in python, hmmm : > > In [1]: from temp import func > > In [2]: func(5) > Out[2]: 5 > > In [3]: def g(s) : return s*2 >...: > > In [4]: func.func_code = g.func_code > > In [5]: func(5) > Out[5]: 10 > > hey, that should work ! Great Construct! Much flexibility! I'll try the implementation tomorrow. - The actual Versions of the hooks can be found here: http://case.lazaridis.com/browser/django/rework/syncdb_hook.py?rev=7 http://case.lazaridis.com/browser/django/rework/startproject_hook.py?rev=13 This construct has helped to simplify nearly all simplification goals: http://case.lazaridis.com/wiki/DjangoSchemaEvolution . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Le Vendredi 09 Juin 2006 20:06, Ilias Lazaridis a écrit : > the code below works, but has the limitation that I cannot import the > syncdb_hook within "django.core.management". In [4]: from b import CONS In [5]: import b In [6]: b.CONS = 3 In [7]: CONS Out[7]: 5 In [8]: from b import CONS In [9]: CONS Out[9]: 3 So, if you change one module name, a function or a class or a constant, you must do it before it is imported, or you must reload modules using it. But either are not always possible, and the later is not what you want to achieve here as it will re-execute all initialisation code in those modules. But think of that, a function is hopefully an object in python, hmmm : In [1]: from temp import func In [2]: func(5) Out[2]: 5 In [3]: def g(s) : return s*2 ...: In [4]: func.func_code = g.func_code In [5]: func(5) Out[5]: 10 hey, that should work ! -- _ Maric Michaud _ Aristote - www.aristote.info 3 place des tapis 69004 Lyon Tel: +33 426 880 097 -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Slawomir Nowaczyk wrote: > On Thu, 08 Jun 2006 15:28:39 +0300 > Ilias Lazaridis <[EMAIL PROTECTED]> wrote: > > #> *IMPORT* > #> > #> I would like to know, if this construct is valid, or if it can > #> result in problems (that I do not see as a newcomer): > > The intricacies of import are far beyond me, but FWIW I do not see > anything wrong in this code. > > #> Is there any way (beside a patch) to alter the behaviour to an > #> existing function. > > You can just assign new function to the old name. There are a few > loops to hop through if you want to alter the behaviour of an existing > *method*... There is an example -- I do not know if a good one -- here: > http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52192 This looks intresting, especially the comment, although I do not understand what is meant by "creates a cycle in the object". " There is a Better Way to Add Methods To Classes, Moshe Zadka, 2001/03/15 This method creates a cycle in the object for no reason at all. The following function will add any function to an instance in a cycle free way: def add_method(self, method, name=None): if name is None: name = method.func_name class new(self.__class__): pass setattr(new, name, method) self.__class__ = new Use as follows: def pretty_str(self): pass add_method(C(), pretty_str, '__str__') " -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Duncan Booth wrote: > Ilias Lazaridis wrote: > >>> #patch_service.py >>> from toto import service >>> >>> def my_impl(self, *args) : >>> old_result = self._old_method(*args) >>> # ... >>> return new_result >>> >>> if not hasattr(service, '_old_method') : >>> service._old_method = service.method >>> service.method = my_impl >>> >>> once this file is imported, all future calls to "method" of service >>> instances will use my_impl. >> Ok, just a small problem when a _function_ is to be hooked. >> >> Looking a the code in the debugger shows that the function "syncdb" is >> correctly overridden. But when the code returns, "syncdb" has again >> it's original value. >> >> Can I import "syncdb" by reference instead by value, thus the change >> 'survives'? > > The difference is that Maric imported the module. To make the change affect > the original model you have to access the function as an attribute of its > module, not by importing the function from the module. ok, I understand. the code below works, but has the limitation that I cannot import the syncdb_hook within "django.core.management". There is no way to import/get "syncdb" but mutable? >> #syncdb_hook.py >> >> from django.rework.evolve import evolvedb >> from django.core.management import syncdb > from django.core import management > >> def syncdb_new(*args) : >> evolvedb() >> syncdb_result = syncdb_old(*args) >> return syncdb_result >> >> if syncdb != syncdb_new: >> syncdb_old = syncdb >> syncdb = syncdb_new >> > if management.syncdb != syncdb_new: > syncdb_old = management.syncdb > management.syncdb = syncdb_new works fine. . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Ilias Lazaridis wrote: >> #patch_service.py >> from toto import service >> >> def my_impl(self, *args) : >> old_result = self._old_method(*args) >> # ... >> return new_result >> >> if not hasattr(service, '_old_method') : >> service._old_method = service.method >> service.method = my_impl >> >> once this file is imported, all future calls to "method" of service >> instances will use my_impl. > > Ok, just a small problem when a _function_ is to be hooked. > > Looking a the code in the debugger shows that the function "syncdb" is > correctly overridden. But when the code returns, "syncdb" has again > it's original value. > > Can I import "syncdb" by reference instead by value, thus the change > 'survives'? The difference is that Maric imported the module. To make the change affect the original model you have to access the function as an attribute of its module, not by importing the function from the module. > > #-- > > > #syncdb_hook.py > > from django.rework.evolve import evolvedb > from django.core.management import syncdb from django.core import management > > def syncdb_new(*args) : > evolvedb() > syncdb_result = syncdb_old(*args) > return syncdb_result > > if syncdb != syncdb_new: > syncdb_old = syncdb > syncdb = syncdb_new > if management.syncdb != syncdb_new: syncdb_old = management.syncdb management.syncdb = syncdb_new -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Maric Michaud wrote: > Le Jeudi 08 Juin 2006 14:28, Ilias Lazaridis a écrit : >> Another possibility is to enlink (hook?) the functionality into an >> existent function >> >> Is there any way (beside a patch) to alter the behaviour to an existing >> function. Is ther a python construct similar to the "alias_method" of Ruby: >> > No, there is no special construct to do this, but we do things very similar > every day in Zope, it's called "monkey patch" : > > #patch_service.py > from toto import service > > def my_impl(self, *args) : > old_result = self._old_method(*args) > # ... > return new_result > > if not hasattr(service, '_old_method') : > service._old_method = service.method > service.method = my_impl > > once this file is imported, all future calls to "method" of service instances > will use my_impl. Ok, just a small problem when a _function_ is to be hooked. Looking a the code in the debugger shows that the function "syncdb" is correctly overridden. But when the code returns, "syncdb" has again it's original value. Can I import "syncdb" by reference instead by value, thus the change 'survives'? #-- #syncdb_hook.py from django.rework.evolve import evolvedb from django.core.management import syncdb def syncdb_new(*args) : evolvedb() syncdb_result = syncdb_old(*args) return syncdb_result if syncdb != syncdb_new: syncdb_old = syncdb syncdb = syncdb_new . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
On Thu, 08 Jun 2006 15:28:39 +0300 Ilias Lazaridis <[EMAIL PROTECTED]> wrote: #> *IMPORT* #> #> I would like to know, if this construct is valid, or if it can #> result in problems (that I do not see as a newcomer): The intricacies of import are far beyond me, but FWIW I do not see anything wrong in this code. #> Is there any way (beside a patch) to alter the behaviour to an #> existing function. You can just assign new function to the old name. There are a few loops to hop through if you want to alter the behaviour of an existing *method*... There is an example -- I do not know if a good one -- here: http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/52192 -- Best wishes, Slawomir Nowaczyk ( [EMAIL PROTECTED] ) Strange how people who don't even know their neighbors are extremely curious to know if there's extra-terrestrial life. -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
On Thu, 08 Jun 2006 06:05:35 -0700 "Tim N. van der Leeuw" <[EMAIL PROTECTED]> wrote: #> Since your question is so much about Django, you might want to ask #> on Django groups. Now *that*, and the rest of your post, was uncalled for. This thread is perfectly on topic for this list and the question asked concerns *Python*, with django being only a use case. -- Best wishes, Slawomir Nowaczyk ( [EMAIL PROTECTED] ) Some drink at the fountain of knowledge. Others just gargle. -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Duncan Booth wrote:
> Ilias Lazaridis wrote:
>
>> I would like to know, if this construct is valid, or if it can result in
>> problems (that I do not see as a newcomer):
>>
>> 1082try:
>> 1083from django.rework.evolve import evolvedb
>> 1084except ImportError:
>> 1085def evolvedb():
>> 1086"Evolve Command Dummy"
>> 1087print 'Command evolvedb not imported'
>> 1088evolvedb.args =''
>
> The only real problem here is that if django.rework.evolve imports
> something else which doesn't exist you get your fallback code instead of
> reporting the error. In other words there is a chance that you could mask a
> deeper problem.
>
> If this worries you then you could do:
>
> try:
> from django.rework.evolve import evolvedb
> except ImportError, e:
> if str(e).rsplit(' ')[-1] != 'django.rework.evolve':
> raise
> ... rest of code here ...
I thin I understand.
If the exception is _not_ caused by 'django.rework.evolve', then it will
be raised, thus I can see what caused it.
Very nice!
.
--
http://lazaridis.com
--
http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Maric Michaud wrote: > Le Jeudi 08 Juin 2006 15:15, Duncan Booth a écrit : >> but the more usual way is just to call the original method directly in the >> base class. >> >> class SqliteAdapter(BaseClass): >> def create_table(self, *args) >> self.table_evolve(*args) >> result = BaseClass.create_table(self, *args) >> return result >> > > Yeah, this the right way to reuse ancestor's implementation of a method. > >> If that isn't what you are trying to achieve you'll have to explain more. > I'm not a ruby programmer, but I understood it like this : the prupose is to > modify the behavior of an existing third-party class, in all application > (even in existing third party modules), without any code modifications > (traditional patch) in those modules. yes, you've understood right. > Your proposal is not as good here, assuming BaseClass is defined in module > toto, you can still do toto.BaseClass = SqliteAdapter, but you must ensure > that this code is imported before any other where classes inherit from > BaseClass. The one I porpose in my other post is robust, several packages can > even patch the same method with no side effects. Your suggestion is most possibly the relevant construct. I'll post a note after changing the implementation. Thank's a lot! . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Tim N. van der Leeuw wrote: [...] http://case.lazaridis.com/wiki/Please . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Le Jeudi 08 Juin 2006 15:15, Duncan Booth a écrit : > but the more usual way is just to call the original method directly in the > base class. > > class SqliteAdapter(BaseClass): > def create_table(self, *args) > self.table_evolve(*args) > result = BaseClass.create_table(self, *args) > return result > Yeah, this the right way to reuse ancestor's implementation of a method. > If that isn't what you are trying to achieve you'll have to explain more. I'm not a ruby programmer, but I understood it like this : the prupose is to modify the behavior of an existing third-party class, in all application (even in existing third party modules), without any code modifications (traditional patch) in those modules. Your proposal is not as good here, assuming BaseClass is defined in module toto, you can still do toto.BaseClass = SqliteAdapter, but you must ensure that this code is imported before any other where classes inherit from BaseClass. The one I porpose in my other post is robust, several packages can even patch the same method with no side effects. -- _ Maric Michaud _ Aristote - www.aristote.info 3 place des tapis 69004 Lyon Tel: +33 426 880 097 -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Since your question is so much about Django, you might want to ask on Django groups. Oops, you're not welcome there anymore, almost forgot. But if merely reading the subject of a posting I already know who's the poster, it's perhaps a bad sign. Further readers of this thread might be interested in the discussions linked from these pages: http://en.wikipedia.org/wiki/Ilias_Lazaridis http://www.encyclopediadramatica.com/index.php/Ilias http://groups.google.com/group/comp.lang.java.softwaretools/tree/browse_frm/thread/f07832cf6d0094f0/ae6315fda51d50a1?rnum=1&hl=en&_done=%2Fgroup%2Fcomp.lang.java.softwaretools%2Fbrowse_frm%2Fthread%2Ff07832cf6d0094f0%2Fae6315fda51d50a1%3Ftvc%3D1%26q%3Dilias+EVALUATION%26#doc_ae6315fda51d50a1 EOT? -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Le Jeudi 08 Juin 2006 14:28, Ilias Lazaridis a écrit : > Another possibility is to enlink (hook?) the functionality into an > existent function > > Is there any way (beside a patch) to alter the behaviour to an existing > function. Is ther a python construct similar to the "alias_method" of Ruby: > No, there is no special construct to do this, but we do things very similar every day in Zope, it's called "monkey patch" : #patch_service.py from toto import service def my_impl(self, *args) : old_result = self._old_method(*args) # ... return new_result if not hasattr(service, '_old_method') : service._old_method = service.method service.method = my_impl once this file is imported, all future calls to "method" of service instances will use my_impl. -- _ Maric Michaud _ Aristote - www.aristote.info 3 place des tapis 69004 Lyon Tel: +33 426 880 097 -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Ilias Lazaridis wrote: > Is there any way (beside a patch) to alter the behaviour to an > existing function. Is ther a python construct similar to the > "alias_method" of Ruby: This is a Python list. Would you care to explain what alias_method does? > > (example from an simple evolution support for a ruby orm) > > #-- > # use "alias_method" to enlink the code > #-- > > > class SqliteAdapter > alias_method :old_create_table, :create_table > def create_table(*args) > table_evolve(*args) > result = old_create_table(*args) > return result > end > end > This looks like alias_method does nothing much more than an assignment. If you want to override a method in a base class then you can do it something like: class SqliteAdapter(BaseClass): old_create_table = BaseClass.create_table def create_table(self, *args) self.table_evolve(*args) result = self.old_create_table(*args) return result but the more usual way is just to call the original method directly in the base class. class SqliteAdapter(BaseClass): def create_table(self, *args) self.table_evolve(*args) result = BaseClass.create_table(self, *args) return result If that isn't what you are trying to achieve you'll have to explain more. -- http://mail.python.org/mailman/listinfo/python-list
Re: CONSTRUCT - Python's way of Ruby's "alias_method"
Ilias Lazaridis wrote:
> I would like to know, if this construct is valid, or if it can result in
> problems (that I do not see as a newcomer):
>
> 1082try:
> 1083from django.rework.evolve import evolvedb
> 1084except ImportError:
> 1085def evolvedb():
> 1086"Evolve Command Dummy"
> 1087print 'Command evolvedb not imported'
> 1088evolvedb.args =''
The only real problem here is that if django.rework.evolve imports
something else which doesn't exist you get your fallback code instead of
reporting the error. In other words there is a chance that you could mask a
deeper problem.
If this worries you then you could do:
try:
from django.rework.evolve import evolvedb
except ImportError, e:
if str(e).rsplit(' ')[-1] != 'django.rework.evolve':
raise
... rest of code here ...
--
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CONSTRUCT - Python's way of Ruby's "alias_method"
I have a few small questions subjecting python functionality, most importantly the "alias_method". - *IMPORT* I would like to know, if this construct is valid, or if it can result in problems (that I do not see as a newcomer): 1082try: 1083from django.rework.evolve import evolvedb 1084except ImportError: 1085def evolvedb(): 1086"Evolve Command Dummy" 1087print 'Command evolvedb not imported' 1088evolvedb.args ='' - *PATCHING* A second problem is, how to make the setup for users (testers) more convenient. Is there e.g. any mechanism to apply a patch in an automated manner (e.g. using a python library)? - *ALIAS_METHOD* The django commands are hard-coded: http://code.djangoproject.com/browser/django/trunk/django/core/management.py#L1180 thus elegant/dynamic additions of commands seem not possible. Another possibility is to enlink (hook?) the functionality into an existent function Is there any way (beside a patch) to alter the behaviour to an existing function. Is ther a python construct similar to the "alias_method" of Ruby: (example from an simple evolution support for a ruby orm) #-- # use "alias_method" to enlink the code #-- class SqliteAdapter alias_method :old_create_table, :create_table def create_table(*args) table_evolve(*args) result = old_create_table(*args) return result end end http://lazaridis.com/case/persist/og-evolve.rb - - - If anyone is interested to verify the results in order to stabelize the simple schema evolution support for django, please review the results here: http://case.lazaridis.com/wiki/DjangoProductEvaluation http://case.lazaridis.com/wiki/DjangoSchemaEvolution http://case.lazaridis.com/browser/django/rework/evolve.py http://case.lazaridis.com/browser/django/rework/add_evolvedb_command.diff . -- http://lazaridis.com -- http://mail.python.org/mailman/listinfo/python-list
