renumbering chapters >= 19

22-dyn-attr-prop/oscon/explore0.py

@@ -0,0 +1,65 @@
+"""
+explore0.py: Script to explore the OSCON schedule feed
+
+# tag::EXPLORE0_DEMO[]
+    >>> import json
+    >>> raw_feed = json.load(open('data/osconfeed.json'))
+    >>> feed = FrozenJSON(raw_feed)  # <1>
+    >>> len(feed.Schedule.speakers)  # <2>
+    357
+    >>> feed.keys()
+    dict_keys(['Schedule'])
+    >>> sorted(feed.Schedule.keys())  # <3>
+    ['conferences', 'events', 'speakers', 'venues']
+    >>> for key, value in sorted(feed.Schedule.items()): # <4>
+    ...     print(f'{len(value):3} {key}')
+    ...
+      1 conferences
+    484 events
+    357 speakers
+     53 venues
+    >>> feed.Schedule.speakers[-1].name  # <5>
+    'Carina C. Zona'
+    >>> talk = feed.Schedule.events[40]
+    >>> type(talk)  # <6>
+    <class 'explore0.FrozenJSON'>
+    >>> talk.name
+    'There *Will* Be Bugs'
+    >>> talk.speakers  # <7>
+    [3471, 5199]
+    >>> talk.flavor  # <8>
+    Traceback (most recent call last):
+      ...
+    KeyError: 'flavor'
+
+# end::EXPLORE0_DEMO[]
+
+"""
+
+# tag::EXPLORE0[]
+from collections import abc
+
+
+class FrozenJSON:
+    """A read-only façade for navigating a JSON-like object
+       using attribute notation
+    """
+
+    def __init__(self, mapping):
+        self.__data = dict(mapping)  # <1>
+
+    def __getattr__(self, name):  # <2>
+        try:
+            return getattr(self.__data, name)  # <3>
+        except AttributeError:
+            return FrozenJSON.build(self.__data[name])  # <4>
+
+    @classmethod
+    def build(cls, obj):  # <5>
+        if isinstance(obj, abc.Mapping):  # <6>
+            return cls(obj)
+        elif isinstance(obj, abc.MutableSequence):  # <7>
+            return [cls.build(item) for item in obj]
+        else:  # <8>
+            return obj
+# end::EXPLORE0[]