[Tutor] Dynamic inheritance?
Hi, I have a number of classes, each of which should inherit from a related superclass in another module: class A(Super.A): ... class B(Super.B): ... class C(Super.C): ... Is there a way to dynamically determine the value of Super at runtime? Background: Depending on certain object attributes which are set during the object initialization, I need to use a different set of templates for the respective object. Example: If a page object belongs to site A, it needs to inherit from the template class SiteA.Page, a gallery object belonging to site B should inherit from SiteB.Gallery etc. The problem is that the template classes are not self contained, i.e. SiteB.Gallery inherits from SiteB.List, SiteB.Base etc. Thanks in advance, Jan -- Any sufficiently advanced technology is insufficiently documented. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
On Sat, 2005-11-19 at 16:45 +0100, Jan Eden wrote: Is there a way to dynamically determine the value of Super at runtime? Background: Depending on certain object attributes which are set during the object initialization, I need to use a different set of templates for the respective object. If you use new style classes, then there is a super function that can be used to automatically resolve a superclass reference. You can force new style classes by: inherit from object easy to see, but repetitive __metaclass__ = typeput before the class statements super(Myclass,self).__init__(...) will search through the inheritance tree and (in this case) invoke __init__. Use __bases__ to run up the inheritance yourself. class A: ... pass ... class B(A): ... pass ... b.__class__.__bases__ (class __main__.A at 0xb7e9311c,) B.__bases__ (class __main__.A at 0xb7e9311c,) The magic class attributes don't get listed by the dir command so you need to search the documentation to find this. http://docs.python.org/lib/specialattrs.html dir(B) ['__doc__', '__module__'] b = B() dir(b) ['__doc__', '__module__'] -- Lloyd Kvam Venix Corp ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
Jan Eden wrote: Hi, I have a number of classes, each of which should inherit from a related superclass in another module: class A(Super.A): ... class B(Super.B): ... class C(Super.C): ... Is there a way to dynamically determine the value of Super at runtime? Background: Depending on certain object attributes which are set during the object initialization, I need to use a different set of templates for the respective object. Sure, just import the correct template module conditionally and give it a new name: if site == 'siteA': import SiteA as Super else import SiteB as Super class A(Super.A): etc. If you need to do the import based on a string use the __import__() function: http://www.python.org/doc/current/lib/built-in-funcs.html The problem is that the template classes are not self contained, i.e. SiteB.Gallery inherits from SiteB.List, SiteB.Base etc. Thanks in advance, I don't see why that is a problem? Kent -- http://www.kentsjohnson.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
Hi Kent, Kent Johnson wrote on 19.11.2005: Jan Eden wrote: Is there a way to dynamically determine the value of Super at runtime? Background: Depending on certain object attributes which are set during the object initialization, I need to use a different set of templates for the respective object. Sure, just import the correct template module conditionally and give it a new name: if site == 'siteA': import SiteA as Super else import SiteB as Super class A(Super.A): etc. If you need to do the import based on a string use the __import__() function: http://www.python.org/doc/current/lib/built-in-funcs.html Excellent. This is exactly what I need. I was not aware of the fact that you can rename modules upon importing them. The problem is that the template classes are not self contained, i.e. SiteB.Gallery inherits from SiteB.List, SiteB.Base etc. Thanks in advance, I don't see why that is a problem? Please disregard the last statement in my first message: There is indeed no problem with this requirement. Thanks for your help, Jan -- Common sense is what tells you that the world is flat. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] How should I store data ?
I want to store data in the shape of (for example): First name, Last name, Age, ... few more characteristics. I must be able to search data by any of this fields. For example, search for age, or name ... etc Also, I want to put option in main program to change (update), add and remove that data. How do I do that (easiest way, please) ? Yahoo! FareChase - Search multiple travel sites in one click. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
On Sat, 2005-11-19 at 15:23 -0800, Danny Yoo wrote: Here's a small example that shows how classes can be treated just like any other value in Python: # def makeYa(superclass): class Ya(superclass): def sayHi(self): superclass.sayHi(self) print ya return Ya Sorry I totally misunderstood. Essentially, you want the super class(es) in the class statement to be variables. It's a good thing Danny and Kent were around. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor -- Lloyd Kvam Venix Corp ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
[Tutor] smtplib alternative???
Hello, I found this script to send mail online. It works fine but requires me to enter an mail server. I'm looking for something else that doesn't require and SMTP server. Having to specify a mail server prohibits me from sending to alternate domains. Thanks in advance smtpserver = 'my.mailserver.com' RECIPIENTS = ['[EMAIL PROTECTED]'] SENDER = '[EMAIL PROTECTED]' mssg = SomeVariable session = smtplib.SMTP(smtpserver) smtpresult = session.sendmail(SENDER, RECIPIENTS, mssg) if smtpresult: errstr = for recip in smtpresult.keys(): errstr = Could not delivery mail to: %s Server said: %s %s %s % (recip, smtpresult[recip][0], smtpresult[recip][1], errstr) raise smtplib.SMTPException, errstr ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
Danny Yoo wrote: Here's a small example that shows how classes can be treated just like any other value in Python: # def makeYa(superclass): class Ya(superclass): def sayHi(self): superclass.sayHi(self) print ya return Ya class ValleyPerson: def sayHi(self): print like, so, oh my gosh, hi? FrankensteinClass = makeYa(ValleyPerson) instance = FrankensteinClass() instance.sayHi() # Yeah, that'll work too :-) Or even def makeAB(moduleContainingSuperClass): class A(moduleContainingSuperClass.A): pass class B(moduleContainingSuperClass.B) pass return A, B A, B = makeAB(siteA) So there's no need to do trickery with conditional imports; Python treats classes as first-class objects that can be passed around. Trickery? ;) It's just using modules as first-class objects that are bound to names same as anything else. Which solution is better depends on whether you want to choose at the module level or with finer control. Kent -- http://www.kentsjohnson.com ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] How should I store data ?
On Sat, 19 Nov 2005, Bojan Raicevic wrote: I want to store data in the shape of (for example): First name, Last name, Age, ... few more characteristics. I must be able to search data by any of this fields. For example, search for age, or name ... etc Also, I want to put option in main program to change (update), add and remove that data. How do I do that (easiest way, please) ? Hi Bojan, If you're not bound to use Python directly, I'd recommend looking into a relational database. Relational databases may solve the problem you're describing: to search by any field, to handle storage and loading, and to support those operations efficiently. There are few free ones available that you can experiment with. One popular one is sqlite. http://www.sqlite.org/ If you want to then write a nice interface around the database, you can take advantage of the pysqlite module: http://initd.org/projects/pysqlite If you have more questions, please feel free to ask. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] smtplib alternative???
On Sat, 19 Nov 2005, Adisegna wrote: I found this script to send mail online. It works fine but requires me to enter an mail server. I'm looking for something else that doesn't require and SMTP server. Having to specify a mail server prohibits me from sending to alternate domains. Hi Adisegna, I've always assumed that emails have to talk with some SMTP server. RFC821 seems to confirm this: http://www.faqs.org/rfcs/rfc821.html so what you're asking, to be able to send mail without an SMTP server, may not be possible. There is an 'smtpd' module that comes with Python: http://www.python.org/doc/lib/module-smtpd.html I'm also not sure I understand the reason you're trying to avoid talking to an outside smtp server. But again, I'm unfamiliar enough with how the SMTP email protocol really works that perhaps I'm just overlooking something. ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Dynamic inheritance?
Kent Johnson wrote on 19.11.2005: Danny Yoo wrote: Here's a small example that shows how classes can be treated just like any other value in Python: # def makeYa(superclass): class Ya(superclass): def sayHi(self): superclass.sayHi(self) print ya return Ya class ValleyPerson: def sayHi(self): print like, so, oh my gosh, hi? FrankensteinClass = makeYa(ValleyPerson) instance = FrankensteinClass() instance.sayHi() # Yeah, that'll work too :-) Or even def makeAB(moduleContainingSuperClass): class A(moduleContainingSuperClass.A): pass class B(moduleContainingSuperClass.B) pass return A, B A, B = makeAB(siteA) So there's no need to do trickery with conditional imports; Python treats classes as first-class objects that can be passed around. Trickery? ;) It's just using modules as first-class objects that are bound to names same as anything else. Which solution is better depends on whether you want to choose at the module level or with finer control. Hm, sounds like there's more than one way to do it. ;-) Thanks a lot for your examples. I hate to confess that I incorrectly described my requirements. It turns out that I am better off with a (variant of the) state design pattern. But I am stuck there, too. The situation is this: For every object, two string attributes are determined during initialization (one being read from a database, the other inherited as a superclass attribute). The first contains the site name, the second the object type. I'd like to set the template attribute to the proper class: import Templates self.site_name = 'SiteA' self.template_type = 'Page' self.template = ??? self.template should refer to Templates.SiteA.Page in this case (where SiteA is a module of package Templates, and Page is a class within that module). Danny already said that classes can be treated just like any other object - but how do I get from a string to a class or module name? Thanks for all your help, and sorry for my ignorance, Jan -- Any sufficiently advanced technology is indistinguishable from a Perl script. - Programming Perl ___ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
