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This article mainly introduces how to use the fabric chain code Python development package. The introduction in the article is very detailed and has certain reference value. Interested friends must read it!

Fabric-chaincode-python development package for Hyperledger Fabric blockchain Python chain code development, support Fabric 1.4 and 2.0, official download address: http://sc.hubwiz.com/codebag/fabric-chaincode-python/.

1. Development package overview

The Fabric-chaincode-ptyon development package contains the following features:

Complete coverage of API interfaces provided by Fabric official development package (go/java/node)

Based on asyncio asynchronous model implementation, concurrency performance is better

Built-in wiz toolbox for quickly building Hyperledger Fabric development environment

Fabric-chaincode-python development package runs in **Python 3.7+** environment, current version 1.0.0, main classes/interfaces and relationships are shown in the following figure:

Fabric-chaincode-python development package main code file list see official website description: sc.hubwiz.com/codebag/fabric-chaincode-python/

2. Quickly launch Fabric networks with Wiz Toolkit

Wiz Toolkit can quickly build a simple Fabric network as a chain code and application development environment, the network contains only a single peer node and order node, the main characteristics are as follows:

Organization and MSPID: Org1/Org1MSP

Channel name: ch2

Chain code name: wizcc

Sort node: 127.0.0.1: 7050

Peer: 127.0.0.1: 7051/7052

Starting Fabric requires three terminals and setting the wiz toolbox environment variables for each of them:

~/fabric-chaincode-python$ source wiz_env.sh

STEP 1: Create a new directory devnet at Terminal 1 to initialize a fabric project:

~/fabric-chaincode-python$ mkdir devnet && cd devnet~/fabric-chaincode-python/devnet$ wiz init

The results were as follows:

STEP 2: Initialize the cryptographic data and channel initialization transaction data of the Fabric network using wiz net reset at terminal 1#:

~/fabric-chaincode-python/devnet$ wiz net reset

The results were as follows:

STEP 3: Start the peer node and the order node of the Fabric network with wiz net start at terminal 1:

~/fabric-chaincode-python/devnet$ wiz net start

The results were as follows:

STEP 4: Use wiz cc start to start the Python chain code preset in wiz toolbox at terminal 2 #:

~/fabric-chaincode-python/devnet$ wiz cc start

The results were as follows:

STEP 5: Use wiz ch start command to create channel ch2 and add peer node to channel at terminal 3 #:

~/fabric-chaincode-python/devnet$ wiz ch start

The results were as follows:

Test chain code: Use wiz admin command to enter the management console at terminal 3 #:

~/fabric-chaincode-python/devnet$ wiz admin

The results were as follows:

Use the peer chaincode query command to test queries for preset chaincodes:

admin@org1> peer chaincode query -n wizcc -c '{"args":[]}' -C ch2

The results were as follows:

Use the peer chaincode invoke command to test transactions with preset chaincodes:

admin@org1> peer chaincode invoke -n wizcc -c '{"args":[]}' -C ch2

The results were as follows:

3. Run the demo Python chain code in the development package

After the Hyperledger Fabric network is launched, we can replace the chain code in devnet directly with the preset demonstration chain code.

For example, to run the token_demo.py example, first press ctrl+c on the 2#terminal to stop the wiz preset chain code, and then enter the fabric-chaincode-python root directory to execute the demo chain code:

~/fabric-chaincode-python$ python3 token_demo.py

Test balance query and transfer in the admin console of Terminal 3:

admin@org1> peer chaincode query -n wizcc -c '{"args":["balance","tommy"]}' -C ch2admin@org1> peer chaincode invoke -n wizcc -c '{"args":["transfer","tommy","jerry","10"]}' -C ch24, Python chaincode development example

The following Python code uses Fabric-chaincode-python to implement the issuance, transfer, and balance query of a simple token. See the comments section for instructions:

from fabric_shim import Shim #introduce fabric_shim class TokenChaincode: #define chain code async def init(self,stub): #Chain code initialization processing await stub.put_state('tommy',b'1000') #Issue 1000 tokens to Tommy await stub.put_state('jerry',b'1000') #Issue 1000 Tokens to Jerry return Shim.success(b'init ok') #return success message async def invoke(self,stub): #Chain code transaction processing fcn, args = stub.get_function_and_parameters() #Get chain code invocation method name and parameter list if fcn == 'reset': #Route according to method name return await self.init(stub) if fcn == 'balance': return await self.balance(stub,args[0]) if fcn == 'transfer': return await self.transfer(stub,args[0],args[1],args[2]) return Shim.error(b'method not supported') #Unknown method name returns error message async def balance(self,stub,account): #Account balance query method value = await stub.get_state(account) #Read balance from ledger return Shim.success(b'balance => ' + value) #Return balance info async def transfer(self,stub,owner,to,value): #Token Transfer Method value = int(value) owner_balance = await stub.get_state(owner) owner_balance = int(owner_balance) - value #Deduct balance of transferor to_balance = await stub.get_state(to) to_balance = int(to_balance) + value #Increase Transfer Balance await stub.put_state(owner, #Update transferor status bytes(str(owner_balance),'utf-8')) await stub.put_state(to,bytes(str(to_balance),'utf-8')) #Update transfer-in status return Shim.success(b'transfer ok') #return success message Shim.start( TokenChaincode() ) #Start Chain Code 5. Python Chain Code Development Kit API List

The list of Shim's main APIs is as follows:

start(): Start chain code

success(): Create a successful response object

error(): Create a failed response object

The main API listing for Chaincode SupportClient is as follows:

chat(): Initiates bidirectional communication flow with peer nodes

The main API listing for ChaincodeStub is as follows:

get_function_and_parameters(): Get chain code invocation method name and parameter list

get_txid(): Get the ID of the chain code calling transaction

get_channel_id(): Get channel ID of chain code calling transaction

get_creator(): Get the user ID of the chain code invocation transaction

get_transient(): Get transient dataset of chain code call transaction

get_tx_timestamp(): Get the timestamp of chain code invocation transaction

get_state(): Gets the state of the specified key on the ledger

put_state(): Update the state of the specified key on the ledger

delete_state(): deletes the state of the specified key on the ledger

set_state_validation_parameter(): Set state validation parameters

get_state_validation_parameter(): Get state validation parameters

get_state_by_range(): Get the state of keys in the specified range on the ledger

get_state_by_range_with_pagination(): Pagination Gets the state of keys within a specified range on the ledger

get_query_result(): Get node rich query result, valid only if couchdb is used as peer node repository

get_query_result_with_pagination(): Pagination gets node rich query result

get_history_for_key(): Get the update history of the specified key on the ledger

invoke_chaincode(): invoke another chaincode

set_event(): Trigger chain code event

create_composite_key(): Create a composite key

split_composite_key(): split composite key, return composite key type and component attribute value

get_state_by_partial_composite_key(): Query the ledger state using partial composite keys

get_state_by_partial_composite_key_with_pagination(): Query ledger state using partial composite key pagination

get_private_data(): Gets the state of the specified key in the specified private dataset

get_private_data_hash(): Gets the state hash of the specified key in the specified private dataset

put_private_data(): updates the state of the specified key in the specified private dataset

delete_private_data(): deletes the specified key from the specified private dataset

set_private_data_validation_parameter(): Set validation parameters for private data

get_private_data_validation_parameter(): Get validation parameters for private data

get_private_data_by_range(): Gets the state of a specified range of keys in a specified private dataset

get_private_data_by_partial_composite_key(): Query private datasets using partial composite keys

get_private_data_query_result(): Gets rich query results for private datasets, valid only when couchdb is enabled

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