Join Features Object of type 'set' is not JSON serializable

[AFackler_NAPSG]

Hello everyone,

I am trying to create a join between 2 hosted feature layers in ArgGIS API for Python (on ArcGIS Online).  I keep receiving a type error and I'm not really sure how to approach it.

Exception: A general error occurred: Object of type 'set' is not JSON serializable

 Here is the code and the output:

joinData = join_features(target_layer=facilities,
join_layer=counties,
output_name="Facility_county_join",
join_operation="JoinOneToOne",
spatial_relationship="",
attribute_relationship=[{"NAME", "Facility"}],
summary_fields=[{"Current_Status", "SUM"}])

TypeError                                 Traceback (most recent call last)
/opt/conda/lib/python3.6/site-packages/arcgis/gis/_impl/_con/_connection.py in post(self, path, params, files, **kwargs)
    662                     if isinstance(v, (dict, list, tuple, bool)):
--> 663                         params[k] = json.dumps(v)
    664                     elif isinstance(v, PropertyMap):

/opt/conda/lib/python3.6/json/__init__.py in dumps(obj, skipkeys, ensure_ascii, check_circular, allow_nan, cls, indent, separators, default, sort_keys, **kw)
    230         default is None and not sort_keys and not kw):
--> 231         return _default_encoder.encode(obj)
    232     if cls is None:

/opt/conda/lib/python3.6/json/encoder.py in encode(self, o)
    198         # equivalent to the PySequence_Fast that ''.join() would do.
--> 199         chunks = self.iterencode(o, _one_shot=True)
    200         if not isinstance(chunks, (list, tuple)):

/opt/conda/lib/python3.6/json/encoder.py in iterencode(self, o, _one_shot)
    256                 self.skipkeys, _one_shot)
--> 257         return _iterencode(o, 0)
    258 

/opt/conda/lib/python3.6/json/encoder.py in default(self, o)
    179         raise TypeError("Object of type '%s' is not JSON serializable" %
--> 180                         o.__class__.__name__)    181 

TypeError: Object of type 'set' is not JSON serializable

During handling of the above exception, another exception occurred:

Exception                                 Traceback (most recent call last)
<ipython-input-26-cf1ae0f3dbb2> in <module>
      5                          spatial_relationship="",
      6                          attribute_relationship=[{"NAME", "Facility"}],
----> 7                          summary_fields=[{"Current_Status", "SUM"}])
/opt/conda/lib/python3.6/site-packages/arcgis/features/summarize_data.py in join_features(target_layer, join_layer, spatial_relationship, spatial_relationship_distance, spatial_relationship_distance_units, attribute_relationship, join_operation, summary_fields, output_name, context, gis, estimate, future)
    640     if 'summary_fields' not in params:
    641         params['summary_fields'] = summary_fields
--> 642     return gis._tools.featureanalysis.join_features(**params)

/opt/conda/lib/python3.6/site-packages/arcgis/_impl/tools.py in join_features(self, target_layer, join_layer, spatial_relationship, spatial_relationship_distance, spatial_relationship_distance_units, attribute_relationship, join_operation, summary_fields, output_name, context, estimate, records_to_match, future)
   2746                                         output_name=output_name,
   2747                                         context=context, gis=self._gis,
-> 2748                                         future=True)   2749         gpjob._is_fa = True
   2750         if future:

<string> in join_features(target_layer, join_layer, spatial_relationship, spatial_relationship_distance, spatial_relationship_distance_units, attribute_relationship, join_operation, summary_fields, records_to_match, output_name, context, join_type, gis, future)

/opt/conda/lib/python3.6/site-packages/arcgis/geoprocessing/_support.py in _execute_gp_tool(gis, task_name, params, param_db, return_values, use_async, url, webtool, add_token, return_messages, future)
    388                 job_info = gptool._con.post(submit_url, gp_params)
    389         else:
--> 390             job_info = gptool._con.post(submit_url, gp_params)
    391         job_id = job_info['jobId']
    392         if future:

/opt/conda/lib/python3.6/site-packages/arcgis/gis/_impl/_con/_connection.py in post(self, path, params, files, **kwargs)
    698                 "URL scheme must be provided: %s" % errMS)
    699         except Exception as e:
--> 700             raise Exception('A general error occurred: %s' % e)
    701         except:
    702             import traceback

Exception: A general error occurred: Object of type 'set' is not JSON serializable

Thank you in advance!

[DanPatterson]

Do you need the { } within the list 

currently you have defined a set within a list.

a = [{"NAME", "Facility"}]

type(a[0])
set

a0 = ["NAME", "Facility"]

type(a0)
list

type(a0[0])
str

[AFackler_NAPSG]

I don't think so. I did some playing around and I think the attribute relationship needs the { }, but now I'm having an error with the summary fields, just saying "Job Failed".

joinData = join_features(target_layer=facilities,
join_layer=counties,
output_name="Facility_county_join",
join_operation="JoinOneToOne",
spatial_relationship="",
attribute_relationship={"NAME", "Facility"},
summary_fields=["Current_Status", "SUM"])

[DanPatterson]

both parameters say a list of dicts.

attribute_relationship  = [{"NAME": "Facility"}]

summary_fields = [{"Current_Status": "SUM"}]

a = [{"NAME": "Facility"}]

type(a)
list

type(a[0])
dict

Of course I can't find any example syntax in the documents, so if it is true, try a list of dict

A colon makes the difference

type({"NAME", "Facility"})
set

type({"NAME": "Facility"})
dict

ADDENDUM

Found an example in their code

summary_fields=[{"statisticType": "Mean", "onStatisticField": "Population"}

aka. a list of dictionary items

[AFackler_NAPSG · Accepted solution]

Okay with some help between @DanPatterson and some documentation here https://developers.arcgis.com/rest/services-reference/join-features.htm I managed to get it working. I was missing some parameters in the attribute relationship. Final code:

joinData = join_features(target_layer=facilities,
join_layer=counties,
output_name="Facility_county_join",
join_operation="JoinOneToOne",
spatial_relationship="",
attribute_relationship=[{"targetField": "NAME", "joinField": "Facility", "operator": "egual"}],
summary_fields=[{"statisticType": "Sum", "onStatisticField": "Current_status"}])

[Anonymous User]

Appreciated for posting your final solution .