Xpath like query for nested python dictionaries

Question

Is there a way to define a XPath type query for nested python dictionaries.

Something like this:

foo = {
  \'spam\':\'eggs\',
  \'morefoo\': {
               


        

Answer 1

Another alternative (besides that suggested by jellybean) is this:

def querydict(d, q):
  keys = q.split('/')
  nd = d
  for k in keys:
    if k == '':
      continue
    if k in nd:
      nd = nd[k]
    else:
      return None
  return nd

foo = {
  'spam':'eggs',
  'morefoo': {
               'bar':'soap',
               'morebar': {'bacon' : 'foobar'}
              }
   }
print querydict(foo, "/morefoo/morebar")

Answer 2

Is there any reason for you to the query it the way like the XPath pattern? As the commenter to your question suggested, it just a dictionary, so you can access the elements in a nest manner. Also, considering that data is in the form of JSON, you can use simplejson module to load it and access the elements too.

There is this project JSONPATH, which is trying to help people do opposite of what you intend to do (given an XPATH, how to make it easily accessible via python objects), which seems more useful.

Answer 3

dict > jmespath

You can use JMESPath which is a query language for JSON, and which has a python implementation.

import jmespath # pip install jmespath

data = {'root': {'section': {'item1': 'value1', 'item2': 'value2'}}}

jmespath.search('root.section.item2', data)
Out[42]: 'value2'

The jmespath query syntax and live examples: http://jmespath.org/tutorial.html

dict > xml > xpath

Another option would be converting your dictionaries to XML using something like dicttoxml and then use regular XPath expressions e.g. via lxml or whatever other library you prefer.

from dicttoxml import dicttoxml  # pip install dicttoxml
from lxml import etree  # pip install lxml

data = {'root': {'section': {'item1': 'value1', 'item2': 'value2'}}}
xml_data = dicttoxml(data, attr_type=False)
Out[43]: b'<?xml version="1.0" encoding="UTF-8" ?><root><root><section><item1>value1</item1><item2>value2</item2></section></root></root>'

tree = etree.fromstring(xml_data)
tree.xpath('//item2/text()')
Out[44]: ['value2']

Json Pointer

Yet another option is Json Pointer which is an IETF spec that has a python implementation:

• https://github.com/stefankoegl/python-json-pointer

From the jsonpointer-python tutorial:

from jsonpointer import resolve_pointer

obj = {"foo": {"anArray": [ {"prop": 44}], "another prop": {"baz": "A string" }}}

resolve_pointer(obj, '') == obj
# True

resolve_pointer(obj, '/foo/another%20prop/baz') == obj['foo']['another prop']['baz']
# True

>>> resolve_pointer(obj, '/foo/anArray/0') == obj['foo']['anArray'][0]
# True

Answer 4

Not exactly beautiful, but you might use sth like

def xpath_get(mydict, path):
    elem = mydict
    try:
        for x in path.strip("/").split("/"):
            elem = elem.get(x)
    except:
        pass

    return elem

This doesn't support xpath stuff like indices, of course ... not to mention the / key trap unutbu indicated.