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import json |
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import copy |
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from datetime import datetime, timedelta |
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from niprov.format import Format |
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class JsonFormat(Format): |
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"""Helper to convert provenance data to and from json encoded strings. |
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""" |
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datetimeFields = []#['acquired','created','added'] |
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timedeltaFields = []#['duration'] |
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def __init__(self, dependencies): |
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super(JsonFormat, self).__init__(dependencies) |
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self.fileExtension = 'json' |
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self.file = dependencies.getFileFactory() |
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def serializeSingle(self, record): |
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""" |
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Convert one provenance item from its native python dict type to |
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a json string. |
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Args: |
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record (dict): The provenance item to convert. |
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Returns: |
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str: Json version of the provenance. |
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""" |
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flat = self._deflate(record.provenance) |
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return json.dumps(flat, cls=DateTimeAwareJSONEncoder) |
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def deserialize(self, jsonRecord): |
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""" |
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Convert one provenance item from its json string version to the |
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native python dictionary format. |
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Args: |
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jsonRecord (str): The provenance item to convert as json-encoded |
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string. |
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Returns: |
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dict: Python dictionary of the provenance. |
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""" |
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provenance = json.loads(jsonRecord, cls=DateTimeAwareJSONDecoder) |
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return self.file.fromProvenance(provenance) |
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def serializeList(self, listOfRecords): |
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""" |
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Convert a list of provenance items from its native list of python dict |
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type to a json string. |
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Args: |
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listOfRecords (list): The provenance items to convert. |
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Returns: |
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str: Json version of the provenance items. |
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""" |
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flatRecords = [self._deflate(r.provenance) for r in listOfRecords] |
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return json.dumps(flatRecords, cls=DateTimeAwareJSONEncoder) |
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def deserializeList(self, jsonListOfRecords): |
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""" |
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Convert a list of provenance items from its json string version to the |
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a list of the native python dictionary format. |
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Args: |
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jsonListOfRecords (str): The provenance items to convert as |
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json-encoded string. |
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Returns: |
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list: Python list of dictionaries of the provenance. |
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""" |
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provenanceList = json.loads(jsonListOfRecords, cls=DateTimeAwareJSONDecoder) |
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return [self.file.fromProvenance(p) for p in provenanceList] |
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def _deflate(self, record): |
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flatRecord = copy.deepcopy(record) |
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if 'args' in record: |
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flatRecord['args'] = [self._strcust(a) for a in record['args']] |
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if 'kwargs' in record: |
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kwargs = record['kwargs'] |
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flatRecord['kwargs'] = {k: self._strcust(kwargs[k]) |
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for k in kwargs.keys()} |
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if '_id' in record: |
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del flatRecord['_id'] |
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return flatRecord |
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def _strcust(self, val): |
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"""Stringify an object that is not of a simple type.""" |
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if not isinstance(val, (str, unicode, int, float, bool, type(None))): |
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return str(val) |
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return val |
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# Taken from http://taketwoprogramming.blogspot.com/2009/06/subclassing-jsonencoder-and-jsondecoder.html |
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class DateTimeAwareJSONEncoder(json.JSONEncoder): |
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""" |
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Converts a python object, where datetime and timedelta objects are converted |
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into objects that can be decoded using the DateTimeAwareJSONDecoder. |
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""" |
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def default(self, obj): |
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if isinstance(obj, datetime): |
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return { |
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'__type__' : 'datetime', |
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'year' : obj.year, |
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'month' : obj.month, |
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'day' : obj.day, |
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'hour' : obj.hour, |
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'minute' : obj.minute, |
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'second' : obj.second, |
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'microsecond' : obj.microsecond, |
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} |
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elif isinstance(obj, timedelta): |
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return { |
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'__type__' : 'timedelta', |
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'days' : obj.days, |
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'seconds' : obj.seconds, |
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'microseconds' : obj.microseconds, |
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} |
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else: |
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return json.JSONEncoder.default(self, obj) |
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class DateTimeAwareJSONDecoder(json.JSONDecoder): |
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""" |
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Converts a json string, where datetime and timedelta objects were converted |
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into objects using the DateTimeAwareJSONEncoder, back into a python object. |
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""" |
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def __init__(self, **kwargs): |
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json.JSONDecoder.__init__(self, object_hook=self.dict_to_object) |
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def dict_to_object(self, d): |
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if '__type__' not in d: |
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return d |
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type = d.pop('__type__') |
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if type == 'datetime': |
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return datetime(**d) |
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elif type == 'timedelta': |
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return timedelta(**d) |
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else: |
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# Oops... better put this back together. |
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d['__type__'] = type |
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return d |
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ilogue /
niprov
