[sqlalchemy] Re: dynamically adding a validates method
PS: the validate(value) method in typedef[name] is a normal method,
throwing exception on errors and returning the value when OK.
On Apr 16, 2:01 pm, lars van gemerden wrote:
> Thank you, i got it working now. For future reference:
>
> Before creating a sa class with something like:
>
> type(typename, (Base,), classdict)
>
> I first create the classdict in which I define columns, __tablename__,
> etc, and validators (relationships I add later).
>
> The validators i create(using a subclass of dict as classdict in the
> type() call, and typedef being an object holding the definition to be
> used to create a sa class/table) with:
>
> def createValidator(self, typedef):
> # get names of attributes to be validated:
> names = [attr.name for attr in typedef.attributes \
> if attr.validates()]
> #create validator method from validating method in the
> attr
> #definition in typedef:
> def validator(obj, name, value):
> return typedef[name].validate(value)
> #turn into sa "@validate" descriptor (i don't get the
> #mechanics completely, but still):
> validates(*names)(validator)
> #add to classdict
> self['validator'] = validator
>
> Hope this helps someone, open to questions ...
>
> Cheers, Lars
>
> On Apr 15, 7:20 pm, Michael Bayer wrote:
>
>
>
>
>
>
>
> > If you can't establish the event at class declaration time, then the
> > @event.listens_for/event.listen() paradigm
> > (seehttp://docs.sqlalchemy.org/en/latest/core/event.htmlforbackground) can
> > be applied to the class-bound attribute (which here is "Positive.value") at
> > any time. "Positive.value" is an attribute generated by the mapping which
> > is a result of using the declarative base.
>
> > On Apr 15, 2012, at 1:10 PM, lars van gemerden wrote:
>
> > > OK, this helps, so how do i do this if i do not know the name of the
> > > attribute to be checked in advance(the "value" in
> > > @validates("value") )?
>
> > > On Apr 15, 6:52 pm, Michael Bayer wrote:
> > >> using type() is equivalent to using a class declaration. The end
> > >> result is the same, as are the mechanics of what goes on both from a
> > >> Python as well as a SQLAlchemy perspective. So this works:
>
> > >> Positive = type("Positive", (Base,), dict(__tablename__ =
> > >> "positives", value = Column(Integer)))
>
> > >> @event.listens_for(Positive.value, "set")
> > >> def checkvalue(target, value, oldvalue, initiator)
> > >> assert value > 0
>
> > >> and also, since type() is equivalent to a class declaration, you can
> > >> still use @validates, if you pass the function into the class
> > >> dictionary, so that it is part of the class before declarative sends it
> > >> off to mapper():
>
> > >> @validates("value")
> > >> def checkvalue(self, name, value):
> > >> assert value > 0
> > >> return value
>
> > >> Positive = type("Positive", (Base,), dict(__tablename__ =
> > >> "positives", value = Column(Integer), checkvalue=checkvalue))
>
> > >> On Apr 15, 2012, at 12:37 PM, lars van gemerden wrote:
>
> > >>> I don't know what "@validates hangs a marker of the method that
> > >>> mapper() uses when it instruments the class" means. I guess my
> > >>> question now becomes: How do I add the event.listens_for descriptor to
> > >>> the class, since i do not have a class declaration in the traditional
> > >>> sense?
>
> > >>> On Apr 15, 4:29 pm, Michael Bayer wrote:
> > @validates hangs a marker of the method that mapper() uses when it
> > instruments the class, so if the class is already mapped then that
> > train has left the station. Taking a cab instead, you can just add
> > the attribute event directly:
>
> > @event.listens_for(Positive.value, "set")
> > def checkvalue(target, value, oldvalue, initiator)
> > assert value > 0
>
> > if you want to return a new, mutated value then add retval=True to
> > listens_for().
>
> > On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>
> > > Hi,
>
> > > I need a way to dynamically add a validates method to a already
> > > created sqla class.
>
> > > In a normal class declaration you can add a validator by:
>
> > > class Positive(Base):
> > > __tablename__ = "positives"
> > > value = Column(Integer)
>
> > > def checkvalue(self, name, value):
> > > assert value > 0
> > > return value
> > > validates("value")(checkvalue)
>
> > > However if you get the class dynamically:
>
> > > Positive = type("Positive", (Base,), dict(__tablename__ =
> > > "positives", value = Column(Integer)))
>
> > > I can't figure out how to add the validator, either in the type() call
> > > or afterwards.
>
> > > Cheers, Lars
>
> > > --
> > > You received this message because you are subscribed to the Google
> > > Groups "sqla
[sqlalchemy] Re: dynamically adding a validates method
Thank you, i got it working now. For future reference:
Before creating a sa class with something like:
type(typename, (Base,), classdict)
I first create the classdict in which I define columns, __tablename__,
etc, and validators (relationships I add later).
The validators i create(using a subclass of dict as classdict in the
type() call, and typedef being an object holding the definition to be
used to create a sa class/table) with:
def createValidator(self, typedef):
# get names of attributes to be validated:
names = [attr.name for attr in typedef.attributes \
if attr.validates()]
#create validator method from validating method in the
attr
#definition in typedef:
def validator(obj, name, value):
return typedef[name].validate(value)
#turn into sa "@validate" descriptor (i don't get the
#mechanics completely, but still):
validates(*names)(validator)
#add to classdict
self['validator'] = validator
Hope this helps someone, open to questions ...
Cheers, Lars
On Apr 15, 7:20 pm, Michael Bayer wrote:
> If you can't establish the event at class declaration time, then the
> @event.listens_for/event.listen() paradigm
> (seehttp://docs.sqlalchemy.org/en/latest/core/event.htmlfor background) can
> be applied to the class-bound attribute (which here is "Positive.value") at
> any time. "Positive.value" is an attribute generated by the mapping which is
> a result of using the declarative base.
>
> On Apr 15, 2012, at 1:10 PM, lars van gemerden wrote:
>
>
>
>
>
>
>
> > OK, this helps, so how do i do this if i do not know the name of the
> > attribute to be checked in advance(the "value" in
> > @validates("value") )?
>
> > On Apr 15, 6:52 pm, Michael Bayer wrote:
> >> using type() is equivalent to using a class declaration. The end result
> >> is the same, as are the mechanics of what goes on both from a Python as
> >> well as a SQLAlchemy perspective. So this works:
>
> >> Positive = type("Positive", (Base,), dict(__tablename__ =
> >> "positives", value = Column(Integer)))
>
> >> @event.listens_for(Positive.value, "set")
> >> def checkvalue(target, value, oldvalue, initiator)
> >> assert value > 0
>
> >> and also, since type() is equivalent to a class declaration, you can still
> >> use @validates, if you pass the function into the class dictionary, so
> >> that it is part of the class before declarative sends it off to mapper():
>
> >> @validates("value")
> >> def checkvalue(self, name, value):
> >> assert value > 0
> >> return value
>
> >> Positive = type("Positive", (Base,), dict(__tablename__ =
> >> "positives", value = Column(Integer), checkvalue=checkvalue))
>
> >> On Apr 15, 2012, at 12:37 PM, lars van gemerden wrote:
>
> >>> I don't know what "@validates hangs a marker of the method that
> >>> mapper() uses when it instruments the class" means. I guess my
> >>> question now becomes: How do I add the event.listens_for descriptor to
> >>> the class, since i do not have a class declaration in the traditional
> >>> sense?
>
> >>> On Apr 15, 4:29 pm, Michael Bayer wrote:
> @validates hangs a marker of the method that mapper() uses when it
> instruments the class, so if the class is already mapped then that train
> has left the station. Taking a cab instead, you can just add the
> attribute event directly:
>
> @event.listens_for(Positive.value, "set")
> def checkvalue(target, value, oldvalue, initiator)
> assert value > 0
>
> if you want to return a new, mutated value then add retval=True to
> listens_for().
>
> On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>
> > Hi,
>
> > I need a way to dynamically add a validates method to a already
> > created sqla class.
>
> > In a normal class declaration you can add a validator by:
>
> > class Positive(Base):
> > __tablename__ = "positives"
> > value = Column(Integer)
>
> > def checkvalue(self, name, value):
> > assert value > 0
> > return value
> > validates("value")(checkvalue)
>
> > However if you get the class dynamically:
>
> > Positive = type("Positive", (Base,), dict(__tablename__ =
> > "positives", value = Column(Integer)))
>
> > I can't figure out how to add the validator, either in the type() call
> > or afterwards.
>
> > Cheers, Lars
>
> > --
> > You received this message because you are subscribed to the Google
> > Groups "sqlalchemy" group.
> > To post to this group, send email to sqlalchemy@googlegroups.com.
> > To unsubscribe from this group, send email to
> > sqlalchemy+unsubscr...@googlegroups.com.
> > For more options, visit this group
> > athttp://groups.google.com/group/sqlalchemy?hl=en.
>
> >>> --
> >>> You received this message because you are subscribed to the G
Re: [sqlalchemy] Re: dynamically adding a validates method
If you can't establish the event at class declaration time, then the
@event.listens_for/event.listen() paradigm (see
http://docs.sqlalchemy.org/en/latest/core/event.html for background) can be
applied to the class-bound attribute (which here is "Positive.value") at any
time. "Positive.value" is an attribute generated by the mapping which is a
result of using the declarative base.
On Apr 15, 2012, at 1:10 PM, lars van gemerden wrote:
> OK, this helps, so how do i do this if i do not know the name of the
> attribute to be checked in advance(the "value" in
> @validates("value") )?
>
>
>
> On Apr 15, 6:52 pm, Michael Bayer wrote:
>> using type() is equivalent to using a class declaration. The end result is
>> the same, as are the mechanics of what goes on both from a Python as well as
>> a SQLAlchemy perspective. So this works:
>>
>> Positive = type("Positive", (Base,), dict(__tablename__ =
>> "positives", value = Column(Integer)))
>>
>> @event.listens_for(Positive.value, "set")
>> def checkvalue(target, value, oldvalue, initiator)
>>assert value > 0
>>
>> and also, since type() is equivalent to a class declaration, you can still
>> use @validates, if you pass the function into the class dictionary, so that
>> it is part of the class before declarative sends it off to mapper():
>>
>> @validates("value")
>> def checkvalue(self, name, value):
>> assert value > 0
>> return value
>>
>> Positive = type("Positive", (Base,), dict(__tablename__ =
>> "positives", value = Column(Integer), checkvalue=checkvalue))
>>
>> On Apr 15, 2012, at 12:37 PM, lars van gemerden wrote:
>>
>>
>>
>>
>>
>>
>>
>>> I don't know what "@validates hangs a marker of the method that
>>> mapper() uses when it instruments the class" means. I guess my
>>> question now becomes: How do I add the event.listens_for descriptor to
>>> the class, since i do not have a class declaration in the traditional
>>> sense?
>>
>>> On Apr 15, 4:29 pm, Michael Bayer wrote:
@validates hangs a marker of the method that mapper() uses when it
instruments the class, so if the class is already mapped then that train
has left the station. Taking a cab instead, you can just add the
attribute event directly:
>>
@event.listens_for(Positive.value, "set")
def checkvalue(target, value, oldvalue, initiator)
assert value > 0
>>
if you want to return a new, mutated value then add retval=True to
listens_for().
>>
On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>>
> Hi,
>>
> I need a way to dynamically add a validates method to a already
> created sqla class.
>>
> In a normal class declaration you can add a validator by:
>>
> class Positive(Base):
>__tablename__ = "positives"
>value = Column(Integer)
>>
>def checkvalue(self, name, value):
>assert value > 0
>return value
>validates("value")(checkvalue)
>>
> However if you get the class dynamically:
>>
> Positive = type("Positive", (Base,), dict(__tablename__ =
> "positives", value = Column(Integer)))
>>
> I can't figure out how to add the validator, either in the type() call
> or afterwards.
>>
> Cheers, Lars
>>
> --
> You received this message because you are subscribed to the Google Groups
> "sqlalchemy" group.
> To post to this group, send email to sqlalchemy@googlegroups.com.
> To unsubscribe from this group, send email to
> sqlalchemy+unsubscr...@googlegroups.com.
> For more options, visit this group
> athttp://groups.google.com/group/sqlalchemy?hl=en.
>>
>>> --
>>> You received this message because you are subscribed to the Google Groups
>>> "sqlalchemy" group.
>>> To post to this group, send email to sqlalchemy@googlegroups.com.
>>> To unsubscribe from this group, send email to
>>> sqlalchemy+unsubscr...@googlegroups.com.
>>> For more options, visit this group
>>> athttp://groups.google.com/group/sqlalchemy?hl=en.
>
> --
> You received this message because you are subscribed to the Google Groups
> "sqlalchemy" group.
> To post to this group, send email to sqlalchemy@googlegroups.com.
> To unsubscribe from this group, send email to
> sqlalchemy+unsubscr...@googlegroups.com.
> For more options, visit this group at
> http://groups.google.com/group/sqlalchemy?hl=en.
>
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[sqlalchemy] Re: dynamically adding a validates method
OK, this helps, so how do i do this if i do not know the name of the
attribute to be checked in advance(the "value" in
@validates("value") )?
On Apr 15, 6:52 pm, Michael Bayer wrote:
> using type() is equivalent to using a class declaration. The end result is
> the same, as are the mechanics of what goes on both from a Python as well as
> a SQLAlchemy perspective. So this works:
>
> Positive = type("Positive", (Base,), dict(__tablename__ =
> "positives", value = Column(Integer)))
>
> @event.listens_for(Positive.value, "set")
> def checkvalue(target, value, oldvalue, initiator)
> assert value > 0
>
> and also, since type() is equivalent to a class declaration, you can still
> use @validates, if you pass the function into the class dictionary, so that
> it is part of the class before declarative sends it off to mapper():
>
> @validates("value")
> def checkvalue(self, name, value):
> assert value > 0
> return value
>
> Positive = type("Positive", (Base,), dict(__tablename__ =
> "positives", value = Column(Integer), checkvalue=checkvalue))
>
> On Apr 15, 2012, at 12:37 PM, lars van gemerden wrote:
>
>
>
>
>
>
>
> > I don't know what "@validates hangs a marker of the method that
> > mapper() uses when it instruments the class" means. I guess my
> > question now becomes: How do I add the event.listens_for descriptor to
> > the class, since i do not have a class declaration in the traditional
> > sense?
>
> > On Apr 15, 4:29 pm, Michael Bayer wrote:
> >> @validates hangs a marker of the method that mapper() uses when it
> >> instruments the class, so if the class is already mapped then that train
> >> has left the station. Taking a cab instead, you can just add the
> >> attribute event directly:
>
> >> @event.listens_for(Positive.value, "set")
> >> def checkvalue(target, value, oldvalue, initiator)
> >> assert value > 0
>
> >> if you want to return a new, mutated value then add retval=True to
> >> listens_for().
>
> >> On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>
> >>> Hi,
>
> >>> I need a way to dynamically add a validates method to a already
> >>> created sqla class.
>
> >>> In a normal class declaration you can add a validator by:
>
> >>> class Positive(Base):
> >>> __tablename__ = "positives"
> >>> value = Column(Integer)
>
> >>> def checkvalue(self, name, value):
> >>> assert value > 0
> >>> return value
> >>> validates("value")(checkvalue)
>
> >>> However if you get the class dynamically:
>
> >>> Positive = type("Positive", (Base,), dict(__tablename__ =
> >>> "positives", value = Column(Integer)))
>
> >>> I can't figure out how to add the validator, either in the type() call
> >>> or afterwards.
>
> >>> Cheers, Lars
>
> >>> --
> >>> You received this message because you are subscribed to the Google Groups
> >>> "sqlalchemy" group.
> >>> To post to this group, send email to sqlalchemy@googlegroups.com.
> >>> To unsubscribe from this group, send email to
> >>> sqlalchemy+unsubscr...@googlegroups.com.
> >>> For more options, visit this group
> >>> athttp://groups.google.com/group/sqlalchemy?hl=en.
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "sqlalchemy" group.
> > To post to this group, send email to sqlalchemy@googlegroups.com.
> > To unsubscribe from this group, send email to
> > sqlalchemy+unsubscr...@googlegroups.com.
> > For more options, visit this group
> > athttp://groups.google.com/group/sqlalchemy?hl=en.
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Re: [sqlalchemy] Re: dynamically adding a validates method
using type() is equivalent to using a class declaration. The end result is
the same, as are the mechanics of what goes on both from a Python as well as a
SQLAlchemy perspective. So this works:
Positive = type("Positive", (Base,), dict(__tablename__ =
"positives", value = Column(Integer)))
@event.listens_for(Positive.value, "set")
def checkvalue(target, value, oldvalue, initiator)
assert value > 0
and also, since type() is equivalent to a class declaration, you can still use
@validates, if you pass the function into the class dictionary, so that it is
part of the class before declarative sends it off to mapper():
@validates("value")
def checkvalue(self, name, value):
assert value > 0
return value
Positive = type("Positive", (Base,), dict(__tablename__ =
"positives", value = Column(Integer), checkvalue=checkvalue))
On Apr 15, 2012, at 12:37 PM, lars van gemerden wrote:
> I don't know what "@validates hangs a marker of the method that
> mapper() uses when it instruments the class" means. I guess my
> question now becomes: How do I add the event.listens_for descriptor to
> the class, since i do not have a class declaration in the traditional
> sense?
>
>
>
> On Apr 15, 4:29 pm, Michael Bayer wrote:
>> @validates hangs a marker of the method that mapper() uses when it
>> instruments the class, so if the class is already mapped then that train has
>> left the station. Taking a cab instead, you can just add the attribute
>> event directly:
>>
>> @event.listens_for(Positive.value, "set")
>> def checkvalue(target, value, oldvalue, initiator)
>>assert value > 0
>>
>> if you want to return a new, mutated value then add retval=True to
>> listens_for().
>>
>> On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>>
>>
>>
>>
>>
>>
>>
>>> Hi,
>>
>>> I need a way to dynamically add a validates method to a already
>>> created sqla class.
>>
>>> In a normal class declaration you can add a validator by:
>>
>>> class Positive(Base):
>>>__tablename__ = "positives"
>>>value = Column(Integer)
>>
>>>def checkvalue(self, name, value):
>>>assert value > 0
>>>return value
>>>validates("value")(checkvalue)
>>
>>> However if you get the class dynamically:
>>
>>> Positive = type("Positive", (Base,), dict(__tablename__ =
>>> "positives", value = Column(Integer)))
>>
>>> I can't figure out how to add the validator, either in the type() call
>>> or afterwards.
>>
>>> Cheers, Lars
>>
>>> --
>>> You received this message because you are subscribed to the Google Groups
>>> "sqlalchemy" group.
>>> To post to this group, send email to sqlalchemy@googlegroups.com.
>>> To unsubscribe from this group, send email to
>>> sqlalchemy+unsubscr...@googlegroups.com.
>>> For more options, visit this group
>>> athttp://groups.google.com/group/sqlalchemy?hl=en.
>
> --
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>
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[sqlalchemy] Re: dynamically adding a validates method
I don't know what "@validates hangs a marker of the method that
mapper() uses when it instruments the class" means. I guess my
question now becomes: How do I add the event.listens_for descriptor to
the class, since i do not have a class declaration in the traditional
sense?
On Apr 15, 4:29 pm, Michael Bayer wrote:
> @validates hangs a marker of the method that mapper() uses when it
> instruments the class, so if the class is already mapped then that train has
> left the station. Taking a cab instead, you can just add the attribute
> event directly:
>
> @event.listens_for(Positive.value, "set")
> def checkvalue(target, value, oldvalue, initiator)
> assert value > 0
>
> if you want to return a new, mutated value then add retval=True to
> listens_for().
>
> On Apr 15, 2012, at 8:22 AM, lars van gemerden wrote:
>
>
>
>
>
>
>
> > Hi,
>
> > I need a way to dynamically add a validates method to a already
> > created sqla class.
>
> > In a normal class declaration you can add a validator by:
>
> > class Positive(Base):
> > __tablename__ = "positives"
> > value = Column(Integer)
>
> > def checkvalue(self, name, value):
> > assert value > 0
> > return value
> > validates("value")(checkvalue)
>
> > However if you get the class dynamically:
>
> > Positive = type("Positive", (Base,), dict(__tablename__ =
> > "positives", value = Column(Integer)))
>
> > I can't figure out how to add the validator, either in the type() call
> > or afterwards.
>
> > Cheers, Lars
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "sqlalchemy" group.
> > To post to this group, send email to sqlalchemy@googlegroups.com.
> > To unsubscribe from this group, send email to
> > sqlalchemy+unsubscr...@googlegroups.com.
> > For more options, visit this group
> > athttp://groups.google.com/group/sqlalchemy?hl=en.
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