How to determine what parameter to pass into substrate.query() to query a storage_function from polkascan's py-substrate-interface?

Question

I am trying to use py-substrate-interface to query the acalaOracle.value for Acala/Karura. Below I show a screenshot of how to get the data using polkadot{js}. Here is the python code I am trying:

url = 'wss://acala-rpc-0.aca-api.network'
substrate = SubstrateInterface(url)
hash = substrate.get_chain_finalised_head()
timestamp = substrate.query(module='Timestamp',storage_function='Now',block_hash=hash).value
block = substrate.get_block_number(hash)
result = substrate.query('AcalaOracle', 'Values', params = [{'Token': 'KSM'}], block_hash = block)

I am getting an error substrateinterface.exceptions.SubstrateRequestException: {'code': -32602, 'message': 'invalid type: integer 1234601, expected a (both 0x-prefixed or not) hex string with length of 64 at line 1 column 7'}, so I am not defining the parameter correctly. Would anyone know how to do that?

I tried to following the examples given in this question, but I still can't figure it out. The following code:

result_map = substrate.query_map('AcalaOracle', 'Values')
print(list(result_map))

returns

[[<scale_info::50(value={'Token': 'ACA'})>, <scale_info::495(value={'value': 264510000000000000, 'timestamp': 1655316318429})>], [<scale_info::50(value={'Token': 'DOT'})>, <scale_info::495(value={'value': 7051400000000000000, 'timestamp': 1655316318429})>]]

but I still don't know what to pass as the parameter.

Answer 1

The call is complaining about you sending an integer. You will be getting an integer from get_block_number which you're passing in a block_hash field:

block = substrate.get_block_number(hash) # this is an integer

result = substrate.query('AcalaOracle', 'Values', params = [{'Token': 'KSM'}], block_hash = block)

Since you already appear to have the hash, simply pass that instead of the block number.

result = substrate.query('AcalaOracle', 'Values', params = [{'Token': 'KSM'}], block_hash = hash) # pass hash here instead

Answer 2

To get more information how to format the paramaters of a specific storage function, you can check out: https://github.com/polkascan/py-substrate-interface#type-information-about-how-to-format-parameters