| 1 | # -*- coding: utf-8 -*-
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| 2 |
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| 3 | import os, json
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| 4 |
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| 5 | class JsonStorage():
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| 6 |
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| 7 | """
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| 8 | Json-based storage.
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| 9 | """
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| 10 |
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| 11 | def __init__(self, path='storage.json'):
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| 12 | if os.path.isdir(path):
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| 13 | raise IOError(path, ' is a directory, exiting')
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| 14 | self.path = path
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| 15 |
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| 16 | def exists(self):
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| 17 | return os.path.exists(self.path)
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| 18 |
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| 19 | def jsonize(self, obj):
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| 20 | """
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| 21 | Convert objects to a dictionary of their representation
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| 22 | Based on the exmplaes from Doyg Hellmann:
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| 23 | http://www.doughellmann.com/PyMOTW/json/#working-with-your-own-types
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| 24 | """
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| 25 | jobj = { '__class__':obj.__class__.__name__,
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| 26 | '__module__':obj.__module__,
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| 27 | }
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| 28 | jobj.update(obj.__dict__)
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| 29 | return jobj
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| 30 |
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| 31 | def dejsonize(self, jobj):
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| 32 | """
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| 33 | Convert some data that has been "jsonized" to the original
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| 34 | python object. Again, based on the examples from Doug Hellmann
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| 35 | """
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| 36 | if '__class__' in jobj:
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| 37 | class_name = jobj.pop('__class__')
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| 38 | module_name = jobj.pop('__module__')
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| 39 | module = __import__(module_name)
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| 40 | class_ = getattr(module, class_name)
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| 41 | args = dict((key.encode('ascii'), value) \
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| 42 | for key, value in jobj.items())
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| 43 | return class_(**args)
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| 44 | return jobj
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| 45 |
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| 46 | def write(self, data):
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| 47 | with open(self.path, 'w') as storage:
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| 48 | json.dump(data, storage, sort_keys=True, indent=4,
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| 49 | default=self.jsonize)
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| 50 | return True
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| 51 | return False
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| 52 |
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| 53 | def read(self):
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| 54 | with open(self.path, 'r') as storage:
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| 55 | try:
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| 56 | data = json.load(storage,object_hook=self.dejsonize)
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| 57 | except ValueError:
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| 58 | # if no json data could be imported, the file could be
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| 59 | # damaged or perhaps it does not containg json-encoded
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| 60 | # data, simply return an empty string
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| 61 | #
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| 62 | # FIXME: we should notify the user about the problem
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| 63 | return ''
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| 64 | return data
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| 65 |
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