Python SCALE Codec Library for Polymesh


Keywords
scale, codec, polkascan, polkadot, substrate, blockchain, polymesh
License
Apache-2.0
Install
pip install polymath-scalecodec==3.0.2

Documentation

This project is forked from https://github.com/polkascan/py-scale-codec

Python Polymath SCALE Codec

Latest Version Supported Python versions

Python Polymath 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 polymath-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"))

Using the type registry updater in your application

To ensure the type registries are in sync with the current runtime of the blockchain, you can use the updater function in your application:

from scalecodec.updater import update_type_registries

# Update type registries with latest version from Github   
try:
    update_type_registries()
except Exception:
    pass

License

https://github.com/PolymathNetwork/py-scale-codec/blob/master/LICENSE