Created
September 10, 2015 21:59
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| """ | |
| ..module:: deltadict | |
| :platform: Linux | |
| :synopsis: Dictionary that saves old key values to disk | |
| .. moduleauthor:: Pedro Rittner <pr273@cornell.edu> | |
| """ | |
| import tempfile | |
| class DeltaDict(dict): | |
| """ | |
| Dictionary with 'write-through' semantics, using a file as backing storage | |
| """ | |
| def __init__(self, backing_file: str=None, **kwargs): | |
| super().__init__(**kwargs) | |
| self.file_p = None | |
| # Either use backing file, if provided, or use a random tmp file | |
| if backing_file is not None: | |
| self.file_p = open(backing_file, 'w+') | |
| else: | |
| self.file_p = tempfile.TemporaryFile('w+') | |
| def __setitem__(self, key, val): | |
| self.file_p.write("{0} := {1}".format(str(key), str(val))) | |
| super().__setitem__(key, val) | |
| def __del__(self): | |
| self.file_p.close() | |
| def main(): | |
| """ Runs a small test """ | |
| my_dict = DeltaDict(backing_file="backing_file.txt") | |
| my_dict[2] = 2 | |
| print(my_dict[2]) | |
| if __name__ == '__main__': | |
| main() |
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