metaprogramming examples

metaprog/oscon-schedule/explore1.py

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+"""
+explore.py: Script to download and explore the OSCON schedule feed
+
+    >>> raw_feed = load_json()
+    >>> feed = FrozenJSON(raw_feed)
+    >>> sorted(feed.Schedule.keys())
+    ['conferences', 'events', 'speakers', 'venues']
+    >>> for key, value in sorted(feed.Schedule.items()):
+    ...     print('{:3} {}'.format(len(value), key))
+    ...
+      1 conferences
+    484 events
+    357 speakers
+     53 venues
+    >>> feed.Schedule.speakers[-1].name
+    'Carina C. Zona'
+    >>> carina = feed.Schedule.speakers[-1]
+    >>> carina.twitter
+    'cczona'
+    >>> feed.Schedule.events[40].name
+    'There *Will* Be Bugs'
+    >>> feed.Schedule.events[40].speakers
+    [3471, 5199]
+
+"""
+
+from urllib.request import urlopen
+import warnings
+import os
+import json
+from collections import abc
+
+URL = 'http://www.oreilly.com/pub/sc/osconfeed'
+JSON_NAME = 'osconfeed.json'
+
+
+def load_json():
+    if not os.path.exists(JSON_NAME):
+        msg = 'downloading {} to {}'.format(URL, JSON_NAME)
+        warnings.warn(msg)
+        with urlopen(URL) as remote, open(JSON_NAME, 'wb') as local:
+            local.write(remote.read())
+
+    with open(JSON_NAME) as fp:
+        return json.load(fp)
+
+
+class FrozenJSON:
+    """A read-only façade for navigating a JSON-like object
+       using attribute notation
+    """
+
+    def __init__(self, mapping):
+        self._data = dict(mapping)
+
+    def __getattr__(self, name):
+        if hasattr(self._data, name):
+            return getattr(self._data, name)
+        else:
+            return FrozenJSON.build(self._data[name])
+
+    @classmethod
+    def build(cls, obj):
+        if isinstance(obj, abc.Mapping):
+            return cls(obj)
+        elif isinstance(obj, abc.MutableSequence):
+            return [cls.build(item) for item in obj]
+        else:
+            return obj