updated chapter 4 and appendix-A files

appendix-A/schedule2.py

@@ -0,0 +1,132 @@
+"""
+schedule2.py: traversing OSCON schedule data
+
+    >>> import shelve
+    >>> db = shelve.open(DB_NAME)
+    >>> if CONFERENCE not in db: load_db(db)
+
+# BEGIN SCHEDULE2_DEMO
+
+    >>> DbRecord.set_db(db)  
+    >>> event = DbRecord.fetch('event.33950')  
+    >>> event  
+    <Event 'There *Will* Be Bugs'>
+    >>> event.venue  
+    <DbRecord serial='venue.1449'>
+    >>> event.venue.name  
+    'Portland 251'
+    >>> for spkr in event.speakers:  
+    ...     print('{0.serial}: {0.name}'.format(spkr))
+    ...
+    speaker.3471: Anna Martelli Ravenscroft
+    speaker.5199: Alex Martelli
+
+# END SCHEDULE2_DEMO
+
+    >>> db.close()
+
+"""
+
+# BEGIN SCHEDULE2_RECORD
+import warnings
+import inspect  
+
+import osconfeed
+
+DB_NAME = 'data/schedule2_db'  
+CONFERENCE = 'conference.115'
+
+
+class Record:
+    def __init__(self, **kwargs):
+        self.__dict__.update(kwargs)
+
+    def __eq__(self, other):  
+        if isinstance(other, Record):
+            return self.__dict__ == other.__dict__
+        else:
+            return NotImplemented
+# END SCHEDULE2_RECORD
+
+
+# BEGIN SCHEDULE2_DBRECORD
+class MissingDatabaseError(RuntimeError):
+    """Raised when a database is required but was not set."""  
+
+
+class DbRecord(Record): 
+
+    __db = None  
+
+    @staticmethod  
+    def set_db(db):
+        DbRecord.__db = db  
+
+    @staticmethod 
+    def get_db():
+        return DbRecord.__db
+
+    @classmethod  
+    def fetch(cls, ident):
+        db = cls.get_db()
+        try:
+            return db[ident]  
+        except TypeError:
+            if db is None:  
+                msg = "database not set; call '{}.set_db(my_db)'"
+                raise MissingDatabaseError(msg.format(cls.__name__))
+            else:  
+                raise
+
+    def __repr__(self):
+        if hasattr(self, 'serial'):  
+            cls_name = self.__class__.__name__
+            return '<{} serial={!r}>'.format(cls_name, self.serial)
+        else:
+            return super().__repr__()  
+# END SCHEDULE2_DBRECORD
+
+
+# BEGIN SCHEDULE2_EVENT
+class Event(DbRecord):  
+
+    @property
+    def venue(self):
+        key = 'venue.{}'.format(self.venue_serial)
+        return self.__class__.fetch(key)  
+
+    @property
+    def speakers(self):
+        if not hasattr(self, '_speaker_objs'):  
+            spkr_serials = self.__dict__['speakers']  
+            fetch = self.__class__.fetch 
+            self._speaker_objs = [fetch('speaker.{}'.format(key))
+                                  for key in spkr_serials]  
+        return self._speaker_objs  
+
+    def __repr__(self):
+        if hasattr(self, 'name'):  
+            cls_name = self.__class__.__name__
+            return '<{} {!r}>'.format(cls_name, self.name)
+        else:
+            return super().__repr__()  
+# END SCHEDULE2_EVENT
+
+
+# BEGIN SCHEDULE2_LOAD
+def load_db(db):
+    raw_data = osconfeed.load()
+    warnings.warn('loading ' + DB_NAME)
+    for collection, rec_list in raw_data['Schedule'].items():
+        record_type = collection[:-1]  
+        cls_name = record_type.capitalize()  
+        cls = globals().get(cls_name, DbRecord)  
+        if inspect.isclass(cls) and issubclass(cls, DbRecord):  
+            factory = cls  
+        else:
+            factory = DbRecord  
+        for record in rec_list:  
+            key = '{}.{}'.format(record_type, record['serial'])
+            record['serial'] = key
+            db[key] = factory(**record)  
+# END SCHEDULE2_LOAD