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""" Identify specific nodes in a JSON document (RFC 6901) """ |
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__author__ = 'Stefan Kögl <[email protected]>' |
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__version__ = '3.0.0' |
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__website__ = 'https://github.com/stefankoegl/python-json-pointer' |
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__license__ = 'Modified BSD License' |
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import copy |
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import re |
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from collections.abc import Mapping, Sequence |
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from itertools import tee, chain |
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_nothing = object() |
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def set_pointer(doc, pointer, value, inplace=True): |
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"""Resolves a pointer against doc and sets the value of the target within doc. |
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With inplace set to true, doc is modified as long as pointer is not the |
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root. |
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>>> obj = {'foo': {'anArray': [ {'prop': 44}], 'another prop': {'baz': 'A string' }}} |
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>>> set_pointer(obj, '/foo/anArray/0/prop', 55) == \ |
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{'foo': {'another prop': {'baz': 'A string'}, 'anArray': [{'prop': 55}]}} |
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True |
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>>> set_pointer(obj, '/foo/yet another prop', 'added prop') == \ |
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{'foo': {'another prop': {'baz': 'A string'}, 'yet another prop': 'added prop', 'anArray': [{'prop': 55}]}} |
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True |
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>>> obj = {'foo': {}} |
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>>> set_pointer(obj, '/foo/a%20b', 'x') == \ |
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{'foo': {'a%20b': 'x' }} |
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True |
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""" |
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pointer = JsonPointer(pointer) |
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return pointer.set(doc, value, inplace) |
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def resolve_pointer(doc, pointer, default=_nothing): |
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""" Resolves pointer against doc and returns the referenced object |
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>>> obj = {'foo': {'anArray': [ {'prop': 44}], 'another prop': {'baz': 'A string' }}, 'a%20b': 1, 'c d': 2} |
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>>> resolve_pointer(obj, '') == obj |
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True |
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>>> resolve_pointer(obj, '/foo') == obj['foo'] |
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True |
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>>> resolve_pointer(obj, '/foo/another prop') == obj['foo']['another prop'] |
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True |
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>>> resolve_pointer(obj, '/foo/another prop/baz') == obj['foo']['another prop']['baz'] |
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True |
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>>> resolve_pointer(obj, '/foo/anArray/0') == obj['foo']['anArray'][0] |
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True |
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>>> resolve_pointer(obj, '/some/path', None) == None |
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True |
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>>> resolve_pointer(obj, '/a b', None) == None |
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True |
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>>> resolve_pointer(obj, '/a%20b') == 1 |
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True |
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>>> resolve_pointer(obj, '/c d') == 2 |
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True |
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>>> resolve_pointer(obj, '/c%20d', None) == None |
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True |
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""" |
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pointer = JsonPointer(pointer) |
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return pointer.resolve(doc, default) |
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def pairwise(iterable): |
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""" Transforms a list to a list of tuples of adjacent items |
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s -> (s0,s1), (s1,s2), (s2, s3), ... |
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>>> list(pairwise([])) |
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[] |
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>>> list(pairwise([1])) |
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[] |
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>>> list(pairwise([1, 2, 3, 4])) |
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[(1, 2), (2, 3), (3, 4)] |
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""" |
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a, b = tee(iterable) |
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for _ in b: |
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break |
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return zip(a, b) |
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class JsonPointerException(Exception): |
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pass |
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class EndOfList(object): |
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"""Result of accessing element "-" of a list""" |
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def __init__(self, list_): |
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self.list_ = list_ |
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def __repr__(self): |
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return '{cls}({lst})'.format(cls=self.__class__.__name__, |
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lst=repr(self.list_)) |
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class JsonPointer(object): |
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"""A JSON Pointer that can reference parts of a JSON document""" |
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_RE_ARRAY_INDEX = re.compile('0|[1-9][0-9]*$') |
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_RE_INVALID_ESCAPE = re.compile('(~[^01]|~$)') |
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def __init__(self, pointer): |
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invalid_escape = self._RE_INVALID_ESCAPE.search(pointer) |
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if invalid_escape: |
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raise JsonPointerException('Found invalid escape {}'.format( |
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invalid_escape.group())) |
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parts = pointer.split('/') |
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if parts.pop(0) != '': |
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raise JsonPointerException('Location must start with /') |
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parts = [unescape(part) for part in parts] |
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self.parts = parts |
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def to_last(self, doc): |
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"""Resolves ptr until the last step, returns (sub-doc, last-step)""" |
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if not self.parts: |
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return doc, None |
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for part in self.parts[:-1]: |
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doc = self.walk(doc, part) |
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return doc, JsonPointer.get_part(doc, self.parts[-1]) |
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def resolve(self, doc, default=_nothing): |
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"""Resolves the pointer against doc and returns the referenced object""" |
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for part in self.parts: |
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try: |
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doc = self.walk(doc, part) |
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except JsonPointerException: |
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if default is _nothing: |
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raise |
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else: |
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return default |
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return doc |
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get = resolve |
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def set(self, doc, value, inplace=True): |
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"""Resolve the pointer against the doc and replace the target with value.""" |
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if len(self.parts) == 0: |
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if inplace: |
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raise JsonPointerException('Cannot set root in place') |
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return value |
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if not inplace: |
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doc = copy.deepcopy(doc) |
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(parent, part) = self.to_last(doc) |
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if isinstance(parent, Sequence) and part == '-': |
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parent.append(value) |
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else: |
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parent[part] = value |
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return doc |
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@classmethod |
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def get_part(cls, doc, part): |
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"""Returns the next step in the correct type""" |
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if isinstance(doc, Mapping): |
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return part |
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elif isinstance(doc, Sequence): |
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if part == '-': |
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return part |
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if not JsonPointer._RE_ARRAY_INDEX.match(str(part)): |
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raise JsonPointerException("'%s' is not a valid sequence index" % part) |
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return int(part) |
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elif hasattr(doc, '__getitem__'): |
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return part |
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else: |
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raise JsonPointerException("Document '%s' does not support indexing, " |
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"must be mapping/sequence or support __getitem__" % type(doc)) |
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def get_parts(self): |
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"""Returns the list of the parts. For example, JsonPointer('/a/b').get_parts() == ['a', 'b']""" |
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return self.parts |
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def walk(self, doc, part): |
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""" Walks one step in doc and returns the referenced part """ |
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part = JsonPointer.get_part(doc, part) |
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assert hasattr(doc, '__getitem__'), "invalid document type %s" % (type(doc),) |
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if isinstance(doc, Sequence): |
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if part == '-': |
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return EndOfList(doc) |
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try: |
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return doc[part] |
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except IndexError: |
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raise JsonPointerException("index '%s' is out of bounds" % (part,)) |
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try: |
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return doc[part] |
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except KeyError: |
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raise JsonPointerException("member '%s' not found in %s" % (part, doc)) |
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def contains(self, ptr): |
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""" Returns True if self contains the given ptr """ |
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return self.parts[:len(ptr.parts)] == ptr.parts |
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def __contains__(self, item): |
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""" Returns True if self contains the given ptr """ |
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return self.contains(item) |
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def join(self, suffix): |
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""" Returns a new JsonPointer with the given suffix append to this ptr """ |
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if isinstance(suffix, JsonPointer): |
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suffix_parts = suffix.parts |
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elif isinstance(suffix, str): |
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suffix_parts = JsonPointer(suffix).parts |
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else: |
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suffix_parts = suffix |
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try: |
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return JsonPointer.from_parts(chain(self.parts, suffix_parts)) |
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except: |
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raise JsonPointerException("Invalid suffix") |
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def __truediv__(self, suffix): |
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return self.join(suffix) |
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@property |
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def path(self): |
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"""Returns the string representation of the pointer |
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>>> ptr = JsonPointer('/~0/0/~1').path == '/~0/0/~1' |
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""" |
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parts = [escape(part) for part in self.parts] |
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return ''.join('/' + part for part in parts) |
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def __eq__(self, other): |
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"""Compares a pointer to another object |
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Pointers can be compared by comparing their strings (or splitted |
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strings), because no two different parts can point to the same |
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structure in an object (eg no different number representations) |
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""" |
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if not isinstance(other, JsonPointer): |
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return False |
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return self.parts == other.parts |
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def __hash__(self): |
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return hash(tuple(self.parts)) |
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def __str__(self): |
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return self.path |
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def __repr__(self): |
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return type(self).__name__ + "(" + repr(self.path) + ")" |
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@classmethod |
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def from_parts(cls, parts): |
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"""Constructs a JsonPointer from a list of (unescaped) paths |
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>>> JsonPointer.from_parts(['a', '~', '/', 0]).path == '/a/~0/~1/0' |
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True |
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""" |
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parts = [escape(str(part)) for part in parts] |
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ptr = cls(''.join('/' + part for part in parts)) |
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return ptr |
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def escape(s): |
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return s.replace('~', '~0').replace('/', '~1') |
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def unescape(s): |
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return s.replace('~1', '/').replace('~0', '~') |
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