Introduction
Gas optimization plays a crucial role in ensuring the efficient execution of smart contracts on the Celo blockchain. By optimizing gas usage, developers can minimize transaction costs and improve overall contract performance. In this tutorial, we will explore how to optimize gas usage in Celo smart contracts using the web3.py library. We will cover steps to estimate gas usage, set gas prices, allocate gas limits, and execute transactions efficiently.
Prerequisites
A basic understanding of the Python programming language is necessary to work with web3.py and implement the code examples provided in the tutorial. Familiarity with the concepts of smart contracts, blockchain technology, and specifically the Celo blockchain will provide a foundation for understanding the gas optimization techniques. You will need access to a Celo network node to connect to the Celo blockchain and interact with smart contracts. This can be a local node running on your machine, a remote node, or a hosted service
Requirements
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VS Code (recommended)
This is a list of what we’ll cover 
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Step 1: Understanding Gas Price -
Step 2: Project setup
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Step 3: Writing a simulation script
Step 1: Understanding Gas Price
Gas price determines how much you are willing to pay for each unit of gas consumed by your transaction. Setting an appropriate gas price can help you optimize your costs. In this step, we will explore the concept of gas price in the context of Celo smart contracts. Gas price represents the amount of cryptocurrency (in wei) that users are willing to pay per unit of gas to have their transactions included in the blockchain. We will learn how to set the gas price using web3.py to optimize transaction fees and balance cost-efficiency with transaction speed.
Step 2: Project setup
First, we will create a new directory for our project and initialize a virtual environment. We will use the virtualenv package to create a virtual environment and install the required dependencies.
# Create a new directory for the project
mkdir gas-optimization && cd gas-optimization
# Create a virtual environment
virtualenv venv
# Activate the virtual environment
source venv/bin/activate
# Install dependencies
pip install web3 python-dotenv
Next, we will create a .env file to store our environment variables. This file will store the mnemonic phrase for our account and the RPC endpoint for the Celo network node. We will use the python-dotenv package to load the environment variables from the .env file.
RPC_URL=<RPC_URL>
MNEMONIC=<MNEMONIC>
Step 3: Writing a simulation script
Next, we will write a script to simulate a transaction and estimate the gas usage. Create a new file named gas_simulation.py and add the following code to it.
from web3 import Web3, HTTPProvider
from web3.middleware import geth_poa_middleware, construct_sign_and_send_raw_middleware
from dotenv import load_dotenv
import os
# Load environment variables
load_dotenv()
First, we import the required packages. We will use the web3.py library to interact with the Celo blockchain. We will use the dotenv package to load the environment variables from the .env file.
# Create web3 instance
w3 = Web3(HTTPProvider(os.getenv("RPC_URL")))
# Load account from mnemonic and set as default account in web3
w3.eth.account.enable_unaudited_hdwallet_features()
account = w3.eth.account.from_mnemonic(os.getenv("MNEMONIC"), account_path="m/44'/60'/0'/0/0")
# Set the default account
w3.eth.default_account = account.address
# Set the middleware
w3.middleware_onion.inject(geth_poa_middleware, layer=0)
w3.middleware_onion.add(construct_sign_and_send_raw_middleware(account._private_key))
# Check connection
print(w3.is_connected())
Next, we create a Web3 instance and load the account from the mnemonic phrase. We will use the account to sign and send transactions to the Celo blockchain. We will also set up the middleware to sign and send transactions using the account. Finally, we will check the connection to the Celo network node. Run the script, and you should see True printed in the terminal.
contract_address = ""
contract_abi = []
contract = w3.eth.contract(address=contract_address, abi=contract_abi)
In this case, we will use the web3.py library to interact with a smart contract deployed on the Celo blockchain for the gas simulation. To interact with the contract, we will need the contract address and ABI. Replace the contract_address and contract_abi variables with the address and ABI of the smart contract you want to interact with.
gas_estimate = contract.functions.faucet().estimate_gas({'from':w3.eth.default_account})
gas_buffer = 100000
gas_limit = gas_estimate + gas_buffer
print("Gas estimate: {}".format(gas_estimate))
print("Gas limit: {}".format(gas_limit))
Next, we will estimate the gas usage for the transaction. We will use the estimate_gas() method to estimate the gas usage for the transaction. We will also add a buffer to the gas estimate to ensure that the transaction does not fail due to insufficient gas. Finally, we will print the gas estimate and gas limit to the terminal.
# Submit transaction
tx_hash = contract.functions.faucet().transact({'from':w3.eth.default_account, 'gas':gas_limit})
print("Gas used: {}".format(w3.eth.wait_for_transaction_receipt(tx_hash)['gasUsed']))
print("Transaction hash: {}".format(tx_hash.hex()))
Finally, we will submit the transaction to the Celo blockchain. We will use the transact() method to submit the transaction. We will also print the gas used and transaction hash to the terminal. Run the script, and you should see the gas estimate, gas limit, gas used, and transaction hash printed in the terminal. You can use the gas estimate and gas limit to optimize the gas usage for your transactions.
Our final script should look like this 
from web3 import Web3, HTTPProvider
from web3.middleware import geth_poa_middleware, construct_sign_and_send_raw_middleware
from dotenv import load_dotenv
import os
load_dotenv()
# Create web3 instance
w3 = Web3(HTTPProvider(os.getenv("RPC_URL")))
# Load account from mnemonic and set as default account in web3
w3.eth.account.enable_unaudited_hdwallet_features()
account = w3.eth.account.from_mnemonic(os.getenv("MNEMONIC"), account_path="m/44'/60'/0'/0/0")
# Set the default account
w3.eth.default_account = account.address
# Set the middleware
w3.middleware_onion.inject(geth_poa_middleware, layer=0)
w3.middleware_onion.add(construct_sign_and_send_raw_middleware(account._private_key))
# Contract Instance
contract_address = "<CONTRACT_ADDRESS>"
constract_abi = [SMART_CONTRACT_ABI]
contract = w3.eth.contract(address=contract_address, abi=constract_abi)
# Estimate gas for request faucet
gas_estimate = contract.functions.faucet().estimate_gas({'from':w3.eth.default_account})
gas_buffer = 100000
gas_limit = gas_estimate + gas_buffer
print("Gas estimate: {}".format(gas_estimate))
print("Gas limit: {}".format(gas_limit))
# Submit transaction
tx_hash = contract.functions.faucet().transact({'from':w3.eth.default_account, 'gas':gas_limit})
print("Gas used: {}".format(w3.eth.wait_for_transaction_receipt(tx_hash)['gasUsed']))
print("Transaction hash: {}".format(tx_hash.hex()))
Conclusion
Gas optimization is a crucial aspect of developing efficient and cost-effective smart contracts on the Celo blockchain. By following the steps outlined in this tutorial and leveraging web3.py, developers can effectively estimate gas usage, set appropriate gas prices and limits, and optimize transaction costs in their Celo smart contracts. Remember to consider factors such as contract complexity, gas price fluctuations, and network congestion while optimizing gas usage. Regular monitoring and analysis will help fine-tune gas optimizations for improved contract performance and reduced costs.
Happy optimizing! 
About the Author
Jimoh Yusuf is a web3 developer and a data scientist with a passion of learning. I will be glad to connect with people who share have same ambition as me on Twitter handle @YusufJi30148537
