# -*- coding: utf-8 -*- # # python-json-patch - An implementation of the JSON Patch format # https://github.com/stefankoegl/python-json-patch # # Copyright (c) 2011 Stefan Kögl # All rights reserved. # # Redistribution and use in source and binary forms, with or without # modification, are permitted provided that the following conditions # are met: # # 1. Redistributions of source code must retain the above copyright # notice, this list of conditions and the following disclaimer. # 2. Redistributions in binary form must reproduce the above copyright # notice, this list of conditions and the following disclaimer in the # documentation and/or other materials provided with the distribution. # 3. The name of the author may not be used to endorse or promote products # derived from this software without specific prior written permission. # # THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR # IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES # OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. # IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT # NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. # """Apply JSON-Patches according to http://tools.ietf.org/html/draft-pbryan-json-patch-01""" # Will be parsed by setup.py to determine package metadata __author__ = 'Stefan Kögl ' __version__ = '0.1' __website__ = 'https://github.com/stefankoegl/python-json-patch' __license__ = 'Modified BSD License' import copy import json class JsonPatchException(Exception): pass def apply_patch(doc, patch): """ >>> obj = { 'baz': 'qux', 'foo': 'bar' } >>> patch = [ { 'remove': '/baz' } ] >>> apply_patch(obj, patch) {'foo': 'bar'} """ p = JsonPatch(patch) return p.apply(doc) class JsonPatch(object): """ A JSON Patch is a list of Patch Operations """ def __init__(self, patch): self.patch = patch self.OPERATIONS = { 'remove': RemoveOperation, 'add': AddOperation, 'replace': ReplaceOperation, } @classmethod def from_string(cls, patch_str): patch = json.loads(patch_str) return cls(patch) def apply(self, obj): """ Applies the patch to a copy of the given object """ obj = copy.deepcopy(obj) for operation in self.patch: op = self._get_operation(operation) op.apply(obj) return obj def _get_operation(self, operation): for action, op_cls in self.OPERATIONS.items(): if action in operation: location = operation[action] op = op_cls(location, operation) return op raise JsonPatchException("invalid operation '%s'" % operation) class PatchOperation(object): """ A single operation inside a JSON Patch """ def __init__(self, location, operation): self.location = location self.operation = operation def locate(self, obj, location, last_must_exist=True): """ Walks through the object according to location Returns the last step as (sub-object, last location-step) """ parts = location.split('/') if parts.pop(0) != '': raise JsonPatchException('location must starts with /') for part in parts[:-1]: obj, loc_part = self._step(obj, part) _, last_loc = self._step(obj, parts[-1], must_exist=last_must_exist) return obj, last_loc def _step(self, obj, loc_part, must_exist=True): """ Goes one step in a locate() call """ # Its not clear if a location "1" should be considered as 1 or "1" # We prefer the integer-variant if possible part_variants = self._try_parse(loc_part) + [loc_part] for variant in part_variants: try: return obj[variant], variant except: continue if must_exist: raise JsonPatchException('key %s not found' % loc_part) else: return obj, part_variants[0] @staticmethod def _try_parse(val, cls=int): try: return [cls(val)] except: return [] class RemoveOperation(PatchOperation): """ Removes an object property or an array element >>> obj = { 'baz': 'qux', 'foo': 'bar' } >>> patch = JsonPatch( [ { 'remove': '/baz' } ] ) >>> patch.apply(obj) {'foo': 'bar'} >>> obj = { 'foo': [ 'bar', 'qux', 'baz' ] } >>> patch = JsonPatch( [ { "remove": "/foo/1" } ] ) >>> patch.apply(obj) {'foo': ['bar', 'baz']} """ def apply(self, obj): subobj, part = self.locate(obj, self.location) del subobj[part] class AddOperation(PatchOperation): """ Adds an object property or an array element >>> obj = { "foo": "bar" } >>> patch = JsonPatch([ { "add": "/baz", "value": "qux" } ]) >>> patch.apply(obj) {'foo': 'bar', 'baz': 'qux'} >>> obj = { "foo": [ "bar", "baz" ] } >>> patch = JsonPatch([ { "add": "/foo/1", "value": "qux" } ]) >>> patch.apply(obj) {'foo': ['bar', 'qux', 'baz']} """ def apply(self, obj): value = self.operation["value"] subobj, part = self.locate(obj, self.location, last_must_exist=False) if isinstance(subobj, list): if part > len(subobj) or part < 0: raise JsonPatchException("can't insert outside of list") subobj.insert(part, value) elif isinstance(subobj, dict): if part in subobj: raise JsonPatchException("object '%s' already exists" % part) subobj[part] = value else: raise JsonPatchException("can't add to type '%s'" % subobj.__class__.__name__) class ReplaceOperation(PatchOperation): """ Replaces a value >>> obj = { "baz": "qux", "foo": "bar" } >>> patch = JsonPatch([ { "replace": "/baz", "value": "boo" } ]) >>> patch.apply(obj) {'foo': 'bar', 'baz': 'boo'} """ def apply(self, obj): location = self. operation["replace"] value = self.operation["value"] subobj, part = self.locate(obj, self.location) if isinstance(subobj, list): if part > len(subobj) or part < 0: raise JsonPatchException("can't replace outside of list") elif isinstance(subobj, dict): if not part in subobj: raise JsonPatchException("can't replace non-existant object '%s'" % part) else: raise JsonPatchException("can't replace in type '%s'" % subobj.__class__.__name__) subobj[part] = value