f3f3410ff9
Let the developer to decide does he wants to modify same object or copy of it. In other way test operation produces huge overhead for nothing.
285 lines
8.4 KiB
Python
285 lines
8.4 KiB
Python
# -*- coding: utf-8 -*-
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#
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# python-json-patch - An implementation of the JSON Patch format
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# https://github.com/stefankoegl/python-json-patch
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#
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# Copyright (c) 2011 Stefan Kögl <stefan@skoegl.net>
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# All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or without
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# modification, are permitted provided that the following conditions
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# are met:
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#
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# 1. Redistributions of source code must retain the above copyright
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# notice, this list of conditions and the following disclaimer.
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# 2. Redistributions in binary form must reproduce the above copyright
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# notice, this list of conditions and the following disclaimer in the
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# documentation and/or other materials provided with the distribution.
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# 3. The name of the author may not be used to endorse or promote products
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# derived from this software without specific prior written permission.
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#
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# THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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# IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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# OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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# IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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# INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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# NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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# THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#
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"""Apply JSON-Patches according to http://tools.ietf.org/html/draft-pbryan-json-patch-04"""
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# Will be parsed by setup.py to determine package metadata
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__author__ = 'Stefan Kögl <stefan@skoegl.net>'
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__version__ = '0.1'
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__website__ = 'https://github.com/stefankoegl/python-json-patch'
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__license__ = 'Modified BSD License'
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import json
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class JsonPatchException(Exception):
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pass
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class JsonPatchConflict(JsonPatchException):
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pass
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def apply_patch(doc, patch):
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"""
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>>> obj = { 'baz': 'qux', 'foo': 'bar' }
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>>> patch = [ { 'remove': '/baz' } ]
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>>> apply_patch(obj, patch)
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{'foo': 'bar'}
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"""
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p = JsonPatch(patch)
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return p.apply(doc)
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class JsonPatch(object):
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""" A JSON Patch is a list of Patch Operations """
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def __init__(self, patch):
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self.patch = patch
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self.OPERATIONS = {
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'remove': RemoveOperation,
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'add': AddOperation,
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'replace': ReplaceOperation,
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'move': MoveOperation,
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'test': TestOperation
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}
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@classmethod
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def from_string(cls, patch_str):
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patch = json.loads(patch_str)
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return cls(patch)
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def apply(self, obj):
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""" Applies the patch to given object """
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for operation in self.patch:
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op = self._get_operation(operation)
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op.apply(obj)
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return obj
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def _get_operation(self, operation):
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for action, op_cls in self.OPERATIONS.items():
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if action in operation:
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location = operation[action]
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op = op_cls(location, operation)
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return op
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raise JsonPatchException("invalid operation '%s'" % operation)
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class PatchOperation(object):
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""" A single operation inside a JSON Patch """
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def __init__(self, location, operation):
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self.location = location
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self.operation = operation
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def locate(self, obj, location, last_must_exist=True):
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""" Walks through the object according to location
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Returns the last step as (sub-object, last location-step) """
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parts = location.split('/')
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if parts.pop(0) != '':
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raise JsonPatchException('location must starts with /')
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for part in parts[:-1]:
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obj, loc_part = self._step(obj, part)
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_, last_loc = self._step(obj, parts[-1], must_exist=last_must_exist)
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return obj, last_loc
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def _step(self, obj, loc_part, must_exist=True):
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""" Goes one step in a locate() call """
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# Its not clear if a location "1" should be considered as 1 or "1"
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# We prefer the integer-variant if possible
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part_variants = self._try_parse(loc_part) + [loc_part]
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for variant in part_variants:
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try:
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return obj[variant], variant
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except:
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continue
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if must_exist:
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raise JsonPatchConflict('key %s not found' % loc_part)
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else:
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return obj, part_variants[0]
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@staticmethod
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def _try_parse(val, cls=int):
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try:
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return [cls(val)]
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except:
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return []
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class RemoveOperation(PatchOperation):
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""" Removes an object property or an array element
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>>> obj = { 'baz': 'qux', 'foo': 'bar' }
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>>> patch = JsonPatch( [ { 'remove': '/baz' } ] )
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>>> patch.apply(obj)
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{'foo': 'bar'}
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>>> obj = { 'foo': [ 'bar', 'qux', 'baz' ] }
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>>> patch = JsonPatch( [ { "remove": "/foo/1" } ] )
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>>> patch.apply(obj)
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{'foo': ['bar', 'baz']}
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"""
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def apply(self, obj):
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subobj, part = self.locate(obj, self.location)
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del subobj[part]
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class AddOperation(PatchOperation):
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""" Adds an object property or an array element
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>>> obj = { "foo": "bar" }
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>>> patch = JsonPatch([ { "add": "/baz", "value": "qux" } ])
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>>> patch.apply(obj)
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{'foo': 'bar', 'baz': 'qux'}
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>>> obj = { "foo": [ "bar", "baz" ] }
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>>> patch = JsonPatch([ { "add": "/foo/1", "value": "qux" } ])
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>>> patch.apply(obj)
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{'foo': ['bar', 'qux', 'baz']}
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"""
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def apply(self, obj):
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value = self.operation["value"]
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subobj, part = self.locate(obj, self.location, last_must_exist=False)
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if isinstance(subobj, list):
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if part > len(subobj) or part < 0:
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raise JsonPatchConflict("can't insert outside of list")
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subobj.insert(part, value)
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elif isinstance(subobj, dict):
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if part in subobj:
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raise JsonPatchConflict("object '%s' already exists" % part)
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subobj[part] = value
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else:
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raise JsonPatchConflict("can't add to type '%s'" % subobj.__class__.__name__)
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class ReplaceOperation(PatchOperation):
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""" Replaces a value
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>>> obj = { "baz": "qux", "foo": "bar" }
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>>> patch = JsonPatch([ { "replace": "/baz", "value": "boo" } ])
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>>> patch.apply(obj)
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{'foo': 'bar', 'baz': 'boo'}
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"""
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def apply(self, obj):
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value = self.operation["value"]
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subobj, part = self.locate(obj, self.location)
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if isinstance(subobj, list):
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if part > len(subobj) or part < 0:
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raise JsonPatchConflict("can't replace outside of list")
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elif isinstance(subobj, dict):
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if not part in subobj:
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raise JsonPatchConflict("can't replace non-existant object '%s'" % part)
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else:
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raise JsonPatchConflict("can't replace in type '%s'" % subobj.__class__.__name__)
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subobj[part] = value
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class MoveOperation(PatchOperation):
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""" Moves a value
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>>> obj = {'foo': {'bar': 'baz', 'waldo': 'fred'}, 'qux': {'corge': 'grault'}}
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>>> patch = JsonPatch([{'move': '/foo/waldo', 'to': '/qux/thud'}])
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>>> patch.apply(obj)
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{'qux': {'thud': 'fred', 'corge': 'grault'}, 'foo': {'bar': 'baz'}}
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>>> obj = {'foo': ['all', 'grass', 'cows', 'eat']}
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>>> patch = JsonPatch([{'move': '/foo/1', 'to': '/foo/3'}])
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>>> patch.apply(obj)
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{'foo': ['all', 'cows', 'eat', 'grass']}
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"""
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def apply(self, obj):
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subobj, part = self.locate(obj, self.location)
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value = subobj[part]
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RemoveOperation(self.location, self.operation).apply(obj)
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AddOperation(self.operation['to'], {'value': value}).apply(obj)
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class TestOperation(PatchOperation):
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""" Test value by specified location
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>>> obj = {'baz': 'qux', 'foo': ['a', 2, 'c']}
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>>> patch = JsonPatch([
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... {'test': '/baz', 'value': 'qux'},
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... {'test': '/foo/1', 'value': 2}
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... ])
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>>> patch.apply(obj)
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{'foo': ['a', 2, 'c'], 'baz': 'qux'}
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>>> patch = JsonPatch([
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... {'test': '/foo/1', 'value': 'BOOM!'}
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... ])
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>>> try:
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... patch.apply(obj)
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... except AssertionError:
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... pass
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... else:
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... assert False, 'test should fall'
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"""
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def apply(self, obj):
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value = self.operation['value']
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subobj, part = self.locate(obj, self.location)
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assert subobj[part] == value
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