Refactor again to try to give Cassette a cleaner interface

vcr/persist.py

@@ -0,0 +1,44 @@
+import tempfile
+import os
+import yaml
+
+# Use the libYAML versions if possible
+try:
+    from yaml import CLoader as Loader, CDumper as Dumper
+except ImportError:
+    from yaml import Loader, Dumper
+
+def _serialize_cassette(requests, responses):
+    '''Return a serializable version of the cassette'''
+    return ([{
+        'request': request,
+        'response': response,
+    } for request, response in zip(requests, responses)])
+
+def _deserialize_cassette(data):
+    requests = [r['request'] for r in data]
+    responses = [r['response'] for r in data]
+    return requests, responses
+
+def _secure_write(path, contents):
+    """
+    We'll overwrite the old version securely by writing out a temporary
+    version and then moving it to replace the old version
+    """
+    dirname, filename = os.path.split(path)
+    fd, name = tempfile.mkstemp(dir=dirname, prefix=filename)
+    with os.fdopen(fd, 'w') as fout:
+        fout.write(contents)
+        os.rename(name, path)
+
+def load_cassette(cassette_path):
+    data =  yaml.load(open(cassette_path), Loader=Loader)
+    return _deserialize_cassette(data)
+
+def save_cassette(cassette_path, requests, responses):
+    dirname, filename = os.path.split(cassette_path)
+    if not os.path.exists(dirname):
+        os.makedirs(dirname)
+    data = _serialize_cassette(requests, responses)
+    data = yaml.dump(data, Dumper=Dumper)
+    _secure_write(cassette_path, data)