ch11-24: clean up by @eumiro & sync with Atlas

23-dyn-attr-prop/oscon/schedule_v5.py

@@ -0,0 +1,89 @@
+"""
+schedule_v5.py: cached properties using functools
+
+    >>> event = Record.fetch('event.33950')
+    >>> event
+    <Event 'There *Will* Be Bugs'>
+    >>> event.venue
+    <Record serial=1449>
+    >>> event.venue_serial
+    1449
+    >>> event.venue.name
+    'Portland 251'
+
+# tag::SCHEDULE3_DEMO[]
+    >>> for spkr in event.speakers:  # <3>
+    ...     print(f'{spkr.serial}: {spkr.name}')
+    ...
+    3471: Anna Martelli Ravenscroft
+    5199: Alex Martelli
+
+# end::SCHEDULE3_DEMO[]
+"""
+
+import json
+import inspect
+
+from functools import cached_property, cache
+
+JSON_PATH = 'data/osconfeed.json'
+
+class Record:
+
+    __index = None
+
+    def __init__(self, **kwargs):
+        self.__dict__.update(kwargs)
+
+    def __repr__(self):
+        cls_name = self.__class__.__name__
+        return f'<{cls_name} serial={self.serial!r}>'
+
+    @staticmethod
+    def fetch(key):
+        if Record.__index is None:
+            Record.__index = load()
+        return Record.__index[key]
+
+
+class Event(Record):
+
+    def __repr__(self):
+        if hasattr(self, 'name'):
+            cls_name = self.__class__.__name__
+            return f'<{cls_name} {self.name!r}>'
+        else:
+            return super().__repr__()
+
+# tag::SCHEDULE5_CACHED_PROPERTY[]
+    @cached_property
+    def venue(self):
+        key = f'venue.{self.venue_serial}'
+        return self.__class__.fetch(key)
+# end::SCHEDULE5_CACHED_PROPERTY[]
+# tag::SCHEDULE5_PROPERTY_OVER_CACHE[]
+    @property  # <1>
+    @cache  # <2>
+    def speakers(self):
+        spkr_serials = self.__dict__['speakers']
+        fetch = self.__class__.fetch
+        return [fetch(f'speaker.{key}')
+                for key in spkr_serials]
+# end::SCHEDULE5_PROPERTY_OVER_CACHE[]
+
+def load(path=JSON_PATH):
+    records = {}
+    with open(path) as fp:
+        raw_data = json.load(fp)
+    for collection, raw_records in raw_data['Schedule'].items():
+        record_type = collection[:-1]
+        cls_name = record_type.capitalize()
+        cls = globals().get(cls_name, Record)
+        if inspect.isclass(cls) and issubclass(cls, Record):
+            factory = cls
+        else:
+            factory = Record
+        for raw_record in raw_records:
+            key = f'{record_type}.{raw_record["serial"]}'
+            records[key] = factory(**raw_record)
+    return records