Part 1. HelloWorld on local emulated environment

Install T-Bears (Docker)

Below command will download tbears docker image, create a container, start the container, and attach your stdin/stderr to the container.

$ docker run -it --name local-tbears -p 9000:9000 iconloop/tbears:mainnet
* Starting RabbitMQ Messaging Server rabbitmq-server [ OK ]
Made tbears_cli_config.json, tbears_server_config.json, keystore_test1 successfully
Started tbears service successfully

Exit and stop the container.

[email protected]:/tbears# exit

Show the container list.

$ docker container ls -a
c5b81f9874ee iconloop/tbears "" 6 minutes ago Up 6 minutes>9000/tcp local-tbears

Start and attach to the container, or attach to a running container.

$ docker container start -a local-tbears
$ docker container attach local-tbears

Test account

Test keystore file, keystore_test1, is provided for your convenience. Be careful not to use this keystore file to sign your transaction to any network other than T-Bears, because the password is open to public.

  • Address : hxe7af5fcfd8dfc67530a01a0e403882687528dfcb

  • Password : test1_Account

  • ICX balance : 0x2961fff8ca4a62327800000

Check your account balance

Let's issue a tbears balance command to check your balance.

[email protected]:/tbears# tbears balance hxe7af5fcfd8dfc67530a01a0e403882687528dfcb
balance in hex: 0x2961fff8ca4a62327800000
balance in decimal: 800460000000000000000000000

Create HelloWorld contract and deploy it

tbears init command will initialize a project.

[email protected]:/tbears# tbears init hello_world HelloWorld
Initialized tbears successfully
[email protected]:/tbears# ls hello_world package.json has the SCORE implementation template which is fully functional.

from iconservice import *
class HelloWorld(IconScoreBase):
def __init__(self, db: IconScoreDatabase) -> None:
def on_install(self) -> None:
def on_update(self) -> None:
def hello(self) -> str:
return "Hello"

Let's deploy the contract without modification and get the contract address. For every transaction, you need to check the execution result using txhash. Transaction result contains the SCORE address if the deployment was successful.

[email protected]:/tbears# tbears deploy hello_world
Send deploy request successfully.
If you want to check SCORE deployed successfully, execute txresult command
transaction hash: 0xc40cbbf2b89cd1e2890132145e6d86ad61835edaca0bcc3a4c34b5cb22b8be28
[email protected]:/tbears# tbears txresult 0xc40cbbf2b89cd1e2890132145e6d86ad61835edaca0bcc3a4c34b5cb22b8be28
Transaction result: {
"jsonrpc": "2.0",
"result": {
"txHash": "0xc40cbbf2b89cd1e2890132145e6d86ad61835edaca0bcc3a4c34b5cb22b8be28",
"blockHeight": "0x3158",
"blockHash": "0x9e0c1385128bf0d425773f9f9130d683d327a058a9c8dc0a6c4df71bb98195e1",
"txIndex": "0x0",
"to": "cx3176b5d6cae66a1abbc3ca9070423a5c708834a9",
"scoreAddress": "cx3176b5d6cae66a1abbc3ca9070423a5c708834a9", <-- SCORE address
"stepUsed": "0x3cdba380",
"stepPrice": "0x2540be400",
"cumulativeStepUsed": "0x3cdba380",
"eventLogs": [],
"logsBloom": "0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
"status": "0x1"
"id": 1

Out of step: contractCreate

If you receive "Out of step" error message, open tbears_cli_config.json and increase the stepLimit value to 0x50000000.

"deploy": {
"stepLimit": "0x50000000",
"mode": "install",
"scoreParams": {}

SCORE has been successfully deployed. We will invoke hello method from CLI and see the result. You need to create a call.json file that contains the request message. to is the SCORE address, from is the message sender's address. Don't forget to provide the actual SCORE address, the one you got after deploy. For the complete json message format, please refer to ICON JSON-RPC API v3 specification.

[email protected]:/tbears# tbears call call.json
response : {
"jsonrpc": "2.0",
"result": "Hello",
"id": 1
[email protected]:/tbears# cat call.json
"jsonrpc": "2.0",
"method": "icx_call",
"id": 1,
"params": {
"from": "hxe7af5fcfd8dfc67530a01a0e403882687528dfcb",
"to": "cx3176b5d6cae66a1abbc3ca9070423a5c708834a9",
"dataType": "call",
"data": {
"method": "hello"

Modify HelloWorld contract to greet you

It would be a pleasure to have a more agreeable HelloWorld SCORE. Let's give it a name, and greet you in a nicer way. One method will be added, hello method will be modified.

  • name is a read-only function and returns the SCORE name.

  • hello method is slightly modified to recognize you. msg is a built-in property that holds information of the message sender, and the amount of ICX the sender attempts to transfer. They can be referenced by msg.sender and msg.value respectively.

def name(self) -> str:
return "HelloWorld"
def hello(self) -> str:
return f'Hello, {self.msg.sender}. My name is {}'

We need to deploy the SCORE again to reflect the change. deploy command with -m update and -o [score_address] options will update the SCORE. Updating is a unique feature of ICON. SCORE address is not changed after the update.

[email protected]:/tbears# tbears deploy -m update -o cx3176b5d6cae66a1abbc3ca9070423a5c708834a9 hello_world
Send deploy request successfully.
If you want to check SCORE deployed successfully, execute txresult command
transaction hash: 0xc412dc9c6685701c8837eddea091283244303d322aa1fba36bc0782e1b483763

Invoke the hello method with the same request message, and see the changes.

[email protected]:/tbears# tbears call call.json
response : {
"jsonrpc": "2.0",
"result": "Hello, hxe7af5fcfd8dfc67530a01a0e403882687528dfcb. My name is HelloWorld",
"id": 1