Easy way to unmarshall/dump objects to Json?

[romainr]

Sorry if I missed it, but could not find it in the documentation or after playing around.

Basically I am trying to get the raw json dump of objects like Tables or TableList, but via the API we are getting many composed objects that need to be unmarshalled manually one by one.

For example: what would be a way to dump into json a TableList? Thanks!

from google.cloud import bigquery
import json

client = bigquery.Client()                
                
for d in client.list_datasets():
  for t in client.list_tables(d.reference):
    print(t)
    print(repr(t))
    print(dir(t))
    print(t.table_id)
    print(json.dumps(t))

<google.cloud.bigquery.table.TableListItem object at 0x7f02c30b0760>
<google.cloud.bigquery.table.TableListItem object at 0x7f02c30b0760>
['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', '_properties', 'clustering_fields', 'created', 'dataset_id', 'expires', 'friendly_name', 'from_string', 'full_table_id', 'labels', 'partition_expiration', 'partitioning_type', 'project', 'reference', 'table_id', 'table_type', 'time_partitioning', 'to_bqstorage', 'view_use_legacy_sql']
arr
Traceback (most recent call last):
  File "<stdin>", line 7, in <module>
  File "/usr/lib/python3.8/json/__init__.py", line 231, in dumps
    return _default_encoder.encode(obj)
  File "/usr/lib/python3.8/json/encoder.py", line 199, in encode
    chunks = self.iterencode(o, _one_shot=True)
  File "/usr/lib/python3.8/json/encoder.py", line 257, in iterencode
    return _iterencode(o, 0)
  File "/usr/lib/python3.8/json/encoder.py", line 179, in default
    raise TypeError(f'Object of type {o.__class__.__name__} '
TypeError: Object of type TableListItem is not JSON serializable
    

-->

{"created":"2020-10-05T01:43:40.077Z","dataset_id":"d","description":null, ...}

[tswast]

2 options for you:

(1) Most objects have a to_api_repr method, which produces a JSON-serilizable value for the class. https://googleapis.dev/python/bigquery/latest/generated/google.cloud.bigquery.job.QueryJobConfig.html#google.cloud.bigquery.job.QueryJobConfig.to_api_repr

(2) It's not a public method, but most objects in this library have a hidden _properties property, which is JSON-serializable. You can try access that.

[tswast]

Looks like TableListItem does not have a to_api_repr method. I'll leave this open as a feature request to add that method there.

https://googleapis.dev/python/bigquery/latest/generated/google.cloud.bigquery.table.TableListItem.html#google.cloud.bigquery.table.TableListItem

[romainr]

I see, this is helpful, thanks a lot! I will use _properties in the meantime.