class DBDB(object):
"""
implement the python dictionary API using concrete BinaryTree implementation
"""
def __init__(self, f):
self._storage = PhysicalObject(f)
# Data stores tend to use more complex types of search trees such as
# B-trees, B+ trees, and others to improve the performance.
self._tree = BinaryTree(self._storage)
def _assert_not_closed(self):
if self._storage.closed:
raise ValueError('Database closed!')
def commit(self):
self._assert_not_closed()
self._tree.commit()
def close(self):
self._storage.close()
def __getitem__(self, key):
self._assert_not_closed()
return self._tree.get(key)
def __setitem__(self, key, value):
self._assert_not_closed()
return self._tree.set(key, value)
def __delitem__(self, key):
self._assert_not_closed()
return self._tree.delete(key)
def __contains__(self, key):
try:
self[key]
except KeyError:
return False
else:
return True
def __len__(self):
return len(self._tree)
def __enter__(self):
pass
def __exit__(self, exc_type, exc_val, exc_tb):
if not self._storage.closed:
self.close()
