def __init__(self, path, basecache=None):
"""
Create a new JSON cache.
Optionally supports populating the cache with values of an
existing cache.
Arguments:
basecache (TransientCache, optional): Cache to populate this new
cache with.
"""
super(JsonCache, self).__init__()
self.path = fs.abspath(path)
if fs.exists(self.path) and fs.Read(self.path):
with open(self.path) as file:
self._data = json.load(file)
if basecache is not None:
for key, val in basecache.items():
self._data[key] = val
# Register exit handler
atexit.register(self.write)
def __contains__(self, key):
"""
Check cache contents.
Arguments:
key: Key.
Returns:
bool: True if key in cache, else false.
"""
path = self.keypath(key)
return fs.exists(path)
def __delitem__(self, key):
"""
Delete cached file.
Arguments:
key: Key.
Raises:
KeyError: If file not in cache.
"""
path = self.keypath(key)
if fs.exists(path):
fs.rm(path)
else:
raise KeyError(key)
def __setitem__(self, key, value):
"""
Emplace file in cache.
Arguments:
key: Key.
value (str): Path of file to insert in cache.
Raises:
ValueError: If no "value" does nto exist.
"""
if not fs.exists(value):
raise ValueError(value)
path = self.keypath(key)
fs.mkdir(self.path)
fs.mv(value, path)
def __getitem__(self, key):
"""
Get path to file in cache.
Arguments:
key: Key.
Returns:
str: Path to cache value.
Raises:
KeyErorr: If key not in cache.
"""
path = self.keypath(key)
if fs.exists(path):
return path
else:
raise KeyError(key)