[Zope] Help with ZODB Howto?

[Sean Holdsworth]

On 23-Nov-99 Michel Pelletier wrote:
>> -----Original Message-----
>> From: Sean Holdsworth [mailto:sh@onyx.net]
>> Sent: Tuesday, November 23, 1999 1:12 PM
>> To: zope@zope.org
>> Subject: [Zope] Help with ZODB Howto?
>> 
>> 
>> Hi All!
>> 
>> Firstly I want to reproduce the functionality of a simple 
>> database that I have
>> written in Python using the shelve module. To this end I've 
>> read up on ZODB and
>> looked at the existing Howto. For experimenting, using the 
>> file storage method
>> is fine. I'm assuming that I can test the code in the Howto 
>> running it outside
>> of the Zope environment as standalone Python (after 
>> correcting the closing
>> bracket typo and adding some wrapper code of course). 
>> Unfortunately this fails
>> miserably 
> 
> How does it fail 'miserably'?  Others have had success with the How-To,
> although I admit it could use some editorial polish.
>

Firstly, apologies if my post implied criticism of the Howto itself; the vast
majority of the Zope howtos that I have looked at, including the one for ZODP,
have provided me with very useful information. I was referring to my own
failure in getting the example code running or even understanding properly
why it was failing.

To provide some details, I simply hacked out the example code from the howto
and added a line to create an instance of the MySimpleZODBApp class as follows:

import Persistence
import ZODB

class Person(Persistence.Persistent):
   """A Persistent Person"""
   def __init__(self, name, age):
           self.name = name
           self.age = age


class MySimpleZODBApp:
   """ A simple application object that manages persistent
   object's of the 'Person' class. """

   def __init__(self, file='Data.fs'):
           """ Create a database, connect to it and get the root
           object out of it.  """

           self.db = ZODB.DB(ZODB.FileStorage(file))
           self.connection = self.db.open()
           self.root = self.connection.root()

           if not len(root):
                   self.root['billy'] = Person('Billy', 77)

                   # normally Zope will handle transactions,
                   # but in this special case, we need to
                   # commit the transaction to save the new
                   # persistent object

                   get_transaction().commit()

   def addPerson(self, name, age):
           """ Adds a 'Person' to the database """
           if self.root.has_key(name):
                   raise 'PersonAllReadyExists', "They're allready there"
           else:
                   self.root[name] = Person(name, age)
                   get_transaction().commit()

   def delPerson(self, name):
           """ Deletes a 'Person' from the database """
           if self.root.has_key(name):
                   del self.root[name]
                   get_transaction().commit()
           else:
                   raise 'NoSuchPerson', 'Who?'

if __name__ == '__main__':
        db = MySimpleZODBApp()

If I run this with the python interpreter that came with the Zope 2.0.1 binary
distribution for Linux x86 I get a traceback as follows:

Traceback (innermost last):
  File "howto.py", line 50, in ?
    db = MySimpleZODBApp()
  File "howto.py", line 19, in __init__
    self.db = ZODB.DB(ZODB.FileStorage(file))
AttributeError: FileStorage

Part of my original question was whether this behavior is a result of interfaces
changing between when the howto was written and as they are in 2.0.1? I know
little of how Zope has evolved and so just wanted to check if
this could be the case or if there is something else I'm not understanding.

Thanks, Sean

  
Sean Holdsworth         | Work: sh@onyx.net          | Zetland Buildings
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