polymath-substrate-interface 3.3.1
Library for interfacing with a Polymesh node
Requires Python: >=3.7, <4
Keywords: interface polkascan polkadot substrate blockchain rpc polymesh

#### This project is forked from https://github.com/polkascan/py-substrate-interface

# Python Polymath Substrate Interface

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Python Polymath Substrate Interface Library

## Description
This library specializes in interfacing with a Polymesh node, providing additional convenience methods to deal with
SCALE encoding/decoding (the default output and input format of the Substrate JSONRPC), metadata parsing, type registry
management and versioning of types.

## Table of Contents

* [Documentation](#documentation)
* [Installation](#installation)
* [Initialization](#hello-world--the-flipper)
  * [Autodiscover mode](#autodiscover-mode)
  * [Manually set required properties](#manually-set-required-properties)  
  * [Substrate Node Template](#substrate-node-template)
* [Features](#features)
  * [Get extrinsics for a certain block](#retrieve-extrinsics-for-a-certain-block)
  * [Subscribe to new block headers](#subscribe-to-new-block-headers)
  * [Storage queries](#storage-queries)
  * [Storage subscriptions](#storage-subscriptions)
  * [Query a mapped storage function](#query-a-mapped-storage-function)
  * [Create and send signed extrinsics](#create-and-send-signed-extrinsics)
  * [Examining the ExtrinsicReceipt object](#examining-the-extrinsicreceipt-object)
  * [ink! contract interfacing](#ink-contract-interfacing)
  * [Create mortal extrinsics](#create-mortal-extrinsics)
  * [Keypair creation and signing](#keypair-creation-and-signing)
  * [Creating keypairs with soft and hard key derivation paths](#creating-keypairs-with-soft-and-hard-key-derivation-paths)
  * [Getting estimate of network fees for extrinsic in advance](#getting-estimate-of-network-fees-for-extrinsic-in-advance)
  * [Offline signing of extrinsics](#offline-signing-of-extrinsics)
  * [Accessing runtime constants](#accessing-runtime-constants)
* [Keeping type registry presets up to date](#keeping-type-registry-presets-up-to-date)
* [Cleanup and context manager](#cleanup-and-context-manager)  
* [License](#license)

## Documentation

https://polkascan.github.io/py-substrate-interface/

## Installation

```bash
pip install polymath-substrate-interface
```

## Initialization

The following examples show how to initialize for Polymesh chain:

Westend

```python
substrate = SubstrateInterface(
    url="wss://westend-rpc.polkadot.io",
    ss58_format=42,
    type_registry_preset='westend'
)
```

### Substrate Node Template
Compatible with https://github.com/substrate-developer-hub/substrate-node-template 

```python
substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    ss58_format=42,
    type_registry_preset='substrate-node-template'
)
 
```

If custom types are introduced in the Substrate chain, the following example will add compatibility by creating a custom type 
registry JSON file and including this during initialization:

```json
{
  "runtime_id": 2,
  "types": {
    "MyCustomInt": "u32",
    "MyStruct": {
      "type": "struct",
      "type_mapping": [
         ["account", "AccountId"],
         ["message", "Vec<u8>"]
      ]
    }
  },
  "versioning": [
  ]
}
```

```python
custom_type_registry = load_type_registry_file("my-custom-types.json")

substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    ss58_format=42,
    type_registry_preset='substrate-node-template',
    type_registry=custom_type_registry
)
 
```

## Keeping type registry presets up to date

When on-chain runtime upgrades occur, types used in call- or storage functions can be added or modified. Therefor it is
important to keep the type registry presets up to date. At the moment the type registry for Polymesh is being actively maintained for this library and an check and update procedure can be triggered with:
 
```python
substrate.update_type_registry_presets()
```   

## Examples

### Get extrinsics for a certain block

```python
# Set block_hash to None for chaintip
block_hash = "0x51d15792ff3c5ee9c6b24ddccd95b377d5cccc759b8e76e5de9250cf58225087"

# Retrieve extrinsics in block
result = substrate.get_block(block_hash=block_hash)

for extrinsic in result['extrinsics']:

    if extrinsic.address:
        signed_by_address = extrinsic.address.value
    else:
        signed_by_address = None

    print('\nPallet: {}\nCall: {}\nSigned by: {}'.format(
        extrinsic.call_module.name,
        extrinsic.call.name,
        signed_by_address
    ))

    # Loop through call params
    for param in extrinsic.params:

        if param['type'] == 'Compact<Balance>':
            param['value'] = '{} {}'.format(param['value'] / 10 ** substrate.token_decimals, substrate.token_symbol)

        print("Param '{}': {}".format(param['name'], param['value']))
```

### Subscribe to new block headers

```python
def subscription_handler(obj, update_nr, subscription_id):

    print(f"New block #{obj['header']['number']} produced by {obj['author']}")

    if update_nr > 10:
        return {'message': 'Subscription will cancel when a value is returned', 'updates_processed': update_nr}


result = substrate.subscribe_block_headers(subscription_handler, include_author=True)
```

### Storage queries
The modules and storage functions are provided in the metadata (see `substrate.get_metadata_storage_functions()`),
parameters will be automatically converted to SCALE-bytes (also including decoding of SS58 addresses).

Example: 

```python
result = substrate.query(
    module='System',
    storage_function='Account',
    params=['F4xQKRUagnSGjFqafyhajLs94e7Vvzvr8ebwYJceKpr8R7T']
)

print(result.value['nonce']) #  7695
print(result.value['data']['free']) # 635278638077956496
```

Or get the account info at a specific block hash:

```python
account_info = substrate.query(
    module='System',
    storage_function='Account',
    params=['F4xQKRUagnSGjFqafyhajLs94e7Vvzvr8ebwYJceKpr8R7T'],
    block_hash='0x176e064454388fd78941a0bace38db424e71db9d5d5ed0272ead7003a02234fa'
)

print(account_info.value['nonce']) #  7673
print(account_info.value['data']['free']) # 637747267365404068
```

### Storage subscriptions

When a callable is passed as kwarg `subscription_handler`, there will be a subscription created for given storage query. 
Updates will be pushed to the callable and will block execution until a final value is returned. This value will be returned
as a result of the query and finally automatically unsubscribed from further updates.

```python
def subscription_handler(account_info_obj, update_nr, subscription_id):

    if update_nr == 0:
        print('Initial account data:', account_info_obj.value)

    if update_nr > 0:
        # Do something with the update
        print('Account data changed:', account_info_obj.value)

    # The execution will block until an arbitrary value is returned, which will be the result of the `query`
    if update_nr > 5:
        return account_info_obj


result = substrate.query("System", "Account", ["5GNJqTPyNqANBkUVMN1LPPrxXnFouWXoe2wNSmmEoLctxiZY"],
                         subscription_handler=subscription_handler)

print(result)
```

### Query a mapped storage function
Mapped storage functions can be iterated over all key/value pairs, for these type of storage functions `query_map` 
can be used.

The result is a `QueryMapResult` object, which is an iterator:

```python
# Retrieve the first 199 System.Account entries
result = substrate.query_map('System', 'Account', max_results=199)

for account, account_info in result:
    print(f"Free balance of account '{account.value}': {account_info.value['data']['free']}")
```

These results are transparantly retrieved in batches capped by the `page_size` kwarg, currently the 
maximum `page_size` restricted by the RPC node is 1000    

```python
# Retrieve all System.Account entries in batches of 200 (automatically appended by `QueryMapResult` iterator)
result = substrate.query_map('System', 'Account', page_size=200, max_results=400)

for account, account_info in result:
    print(f"Free balance of account '{account.value}': {account_info.value['data']['free']}")
```

Querying a `DoubleMap` storage function:

```python
era_stakers = substrate.query_map(
    module='Staking',
    storage_function='ErasStakers',
    params=[2100]
)
```

### Create and send signed extrinsics

The following code snippet illustrates how to create a call, wrap it in a signed extrinsic and send it to the network:

```python
from substrateinterface import SubstrateInterface, Keypair
from substrateinterface.exceptions import SubstrateRequestException

substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    ss58_format=42,
    type_registry_preset='kusama'
)

keypair = Keypair.create_from_mnemonic('episode together nose spoon dose oil faculty zoo ankle evoke admit walnut')

call = substrate.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': '5E9oDs9PjpsBbxXxRE9uMaZZhnBAV38n2ouLB28oecBDdeQo',
        'value': 1 * 10**12
    }
)

extrinsic = substrate.create_signed_extrinsic(call=call, keypair=keypair)

try:
    receipt = substrate.submit_extrinsic(extrinsic, wait_for_inclusion=True)
    print("Extrinsic '{}' sent and included in block '{}'".format(receipt.extrinsic_hash, receipt.block_hash))

except SubstrateRequestException as e:
    print("Failed to send: {}".format(e))
```

The `wait_for_inclusion` keyword argument used in the example above will block giving the result until it gets 
confirmation from the node that the extrinsic is succesfully included in a block. The `wait_for_finalization` keyword
will wait until extrinsic is finalized. Note this feature is only available for websocket connections. 

### Examining the ExtrinsicReceipt object

The `substrate.submit_extrinsic` example above returns an `ExtrinsicReceipt` object, which contains information about the on-chain 
execution of the extrinsic. Because the `block_hash` is necessary to retrieve the triggered events from storage, most
information is only available when `wait_for_inclusion=True` or `wait_for_finalization=True` is used when submitting
an extrinsic. 


Examples:
```python
receipt = substrate.submit_extrinsic(extrinsic, wait_for_inclusion=True)
print(receipt.is_success) # False
print(receipt.weight) # 216625000
print(receipt.total_fee_amount) # 2749998966
print(receipt.error_message['name']) # 'LiquidityRestrictions'
```

`ExtrinsicReceipt` objects can also be created for all existing extrinsics on-chain:

```python

receipt = ExtrinsicReceipt(
    substrate=substrate,
    extrinsic_hash="0x56fea3010910bd8c0c97253ffe308dc13d1613b7e952e7e2028257d2b83c027a",
    block_hash="0x04fb003f8bc999eeb284aa8e74f2c6f63cf5bd5c00d0d0da4cd4d253a643e4c9"
)

print(receipt.is_success) # False
print(receipt.extrinsic.call_module.name) # 'Identity'
print(receipt.extrinsic.call.name) # 'remove_sub'
print(receipt.weight) # 359262000
print(receipt.total_fee_amount) # 2483332406
print(receipt.error_message['docs']) # [' Sender is not a sub-account.']

for event in receipt.triggered_events:
    print(f'* {event.value}')
```

### ink! contract interfacing

#### Deploy a contract 

Tested on [canvas-node](https://github.com/paritytech/canvas-node) with the [Flipper contract from the tutorial](https://substrate.dev/substrate-contracts-workshop/#/0/deploy-contract)_:

```python
substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    type_registry_preset='canvas'
)

keypair = Keypair.create_from_uri('//Alice')

# Deploy contract
code = ContractCode.create_from_contract_files(
    metadata_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.json'),
    wasm_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.wasm'),
    substrate=substrate
)

contract = code.deploy(
    keypair=keypair,
    endowment=10 ** 15,
    gas_limit=1000000000000,
    constructor="new",
    args={'init_value': True},
    upload_code=True
)

print(f'✅ Deployed @ {contract.contract_address}')
```

#### Work with an existing instance:

```python
# Create contract instance from deterministic address
contract = ContractInstance.create_from_address(
    contract_address=contract_address,
    metadata_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.json'),
    substrate=substrate
)
```

#### Read data from a contract:

```python
result = contract.read(keypair, 'get')
print('Current value of "get":', result.contract_result_data)
```

#### Execute a contract call

```python
 # Do a gas estimation of the message
gas_predit_result = contract.read(keypair, 'flip')

print('Result of dry-run: ', gas_predit_result.contract_result_data)
print('Gas estimate: ', gas_predit_result.gas_consumed)

# Do the actual transfer
print('Executing contract call...')
contract_receipt = contract.exec(keypair, 'flip', args={

}, gas_limit=gas_predit_result.gas_consumed)

print(f'Events triggered in contract: {contract_receipt.contract_events}')
```

See complete [code example](https://github.com/polkascan/py-substrate-interface/blob/master/examples/create_and_exec_contract.py) for more details


### Create mortal extrinsics

By default, _immortal_ extrinsics are created, which means they have an indefinite lifetime for being included in a 
block. However, it is recommended to use specify an expiry window, so you know after a certain amount of time if the 
extrinsic is not included in a block, it will be invalidated.

```python 
extrinsic = substrate.create_signed_extrinsic(call=call, keypair=keypair, era={'period': 64})
```

The `period` specifies the number of blocks the extrinsic is valid counted from current head.


### Keypair creation and signing

```python
mnemonic = Keypair.generate_mnemonic()
keypair = Keypair.create_from_mnemonic(mnemonic)
signature = keypair.sign("Test123")
if keypair.verify("Test123", signature):
    print('Verified')
```

By default, a keypair is using SR25519 cryptography, alternatively ED25519 can be explictly specified:

```python
keypair = Keypair.create_from_mnemonic(mnemonic, crypto_type=KeypairType.ED25519)
```

### Creating keypairs with soft and hard key derivation paths

```python
mnemonic = Keypair.generate_mnemonic()
keypair = Keypair.create_from_uri(mnemonic + '//hard/soft')
```

By omitting the mnemonic the default development mnemonic is used: 

```python
keypair = Keypair.create_from_uri('//Alice')
```

### Getting estimate of network fees for extrinsic in advance

```python
keypair = Keypair(ss58_address="EaG2CRhJWPb7qmdcJvy3LiWdh26Jreu9Dx6R1rXxPmYXoDk")

call = substrate.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': 'EaG2CRhJWPb7qmdcJvy3LiWdh26Jreu9Dx6R1rXxPmYXoDk',
        'value': 2 * 10 ** 3
    }
)
payment_info = substrate.get_payment_info(call=call, keypair=keypair)
# {'class': 'normal', 'partialFee': 2499999066, 'weight': 216625000}
```

### Offline signing of extrinsics

This example generates a signature payload which can be signed on another (offline) machine and later on sent to the 
network with the generated signature.

- Generate signature payload on online machine:
```python
substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    ss58_format=42,
    type_registry_preset='substrate-node-template',
)

call = substrate.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY',
        'value': 2 * 10**8
    }
)

era = {'period': 64, 'current': 22719}
nonce = 0

signature_payload = substrate.generate_signature_payload(call=call, era=era, nonce=nonce)
```

- Then on another (offline) machine generate the signature with given `signature_payload`:

```python
keypair = Keypair.create_from_mnemonic("nature exchange gasp toy result bacon coin broccoli rule oyster believe lyrics")
signature = keypair.sign(signature_payload)
```

- Finally on the online machine send the extrinsic with generated signature:

```python
keypair = Keypair(ss58_address="5EChUec3ZQhUvY1g52ZbfBVkqjUY9Kcr6mcEvQMbmd38shQL")

extrinsic = substrate.create_signed_extrinsic(
    call=call,
    keypair=keypair,
    era=era,
    nonce=nonce,
    signature=signature
)

result = substrate.submit_extrinsic(
    extrinsic=extrinsic
)

print(result.extrinsic_hash)
```

### Accessing runtime constants
All runtime constants are provided in the metadata (see `substrate.get_metadata_constants()`),
to access these as a decoded `ScaleType` you can use the function `substrate.get_constant()`:

```python

constant = substrate.get_constant("Balances", "ExistentialDeposit")

print(constant.value) # 10000000000
```

## Cleanup and context manager

At the end of the lifecycle of a `SubstrateInterface` instance, calling the `close()` method will do all the necessary 
cleanup, like closing the websocket connection.

When using the context manager this will be done automatically:

```python
with SubstrateInterface(url="wss://rpc.polkadot.io") as substrate:
    events = substrate.query("System", "Events")

# connection is now closed
```

## Keeping type registry presets up to date

When on-chain runtime upgrades occur, types used in call- or storage functions can be added or modified. Therefor it is
important to keep the type registry presets up to date, otherwise this can lead to decoding errors like 
`RemainingScaleBytesNotEmptyException`. 

At the moment the type registry presets for Polkadot, Kusama, Rococo and
Westend are being actively maintained for this library, and a check and update procedure can be triggered with:
 
```python
substrate.reload_type_registry()
```

This will also activate the updated preset for the current instance.

It is also possible to always use 
the remote type registry preset from Github with the `use_remote_preset` kwarg when instantiating:

```python
substrate = SubstrateInterface(
    url="wss://rpc.polkadot.io",
    ss58_format=0,
    type_registry_preset='polkadot',
    use_remote_preset=True
)
```

To check for updates after instantiating the `substrate` object, using `substrate.reload_type_registry()` will download 
the most recent type registry preset from Github and apply changes to current object.  

## License

https://github.com/PolymathNetwork/py-substrate-interface/blob/master/LICENSE