Python SCALE Codec

Python SCALE Codec Library

Description

Most of the data that the Substrate RPCs output is encoded with the SCALE Codec. This codec is used by the Substrate nodes' internal runtime. In order to get to meaningful data this data will need to be decoded. The Python SCALE Codec Library will specialize in this task.

Documentation

https://polkascan.github.io/py-scale-codec/

Installation

pip install scalecodec

Examples

Decode a SCALE-encoded Compact<Balance>

RuntimeConfiguration().update_type_registry(load_type_registry_preset("default"))
RuntimeConfiguration().update_type_registry(load_type_registry_preset("kusama"))
obj = ScaleDecoder.get_decoder_class('Compact<Balance>', ScaleBytes("0x130080cd103d71bc22"))
obj.decode()
print(obj.value)

Encode to Compact<Balance>

RuntimeConfiguration().update_type_registry(load_type_registry_preset("default"))
obj = ScaleDecoder.get_decoder_class('Compact<Balance>')
scale_data = obj.encode(2503000000000000000)
print(scale_data)

Encode to Vec<Bytes>

RuntimeConfiguration().update_type_registry(load_type_registry_preset("default"))
value = ['test', 'vec']
obj = ScaleDecoder.get_decoder_class('Vec<Bytes>')
scale_data = obj.encode(value)
print(scale_data)

Add custom types to type registry

RuntimeConfiguration().update_type_registry(load_type_registry_preset("default"))

custom_types = {
    "types": {
        "MyCustomType": "u32",
        "CustomNextAuthority": {
          "type": "struct",
          "type_mapping": [
             ["AuthorityId", "AuthorityId"],
             ["weight", "AuthorityWeight"]
          ]
        }
    }   
}

RuntimeConfiguration().update_type_registry(custom_types)

Or from a custom JSON file

RuntimeConfiguration().update_type_registry(load_type_registry_preset("default"))
RuntimeConfiguration().update_type_registry(load_type_registry_file("/path/to/type_registry.json"))

License