Developing Smart Contracts on Ethereum Using Python and Vyper

If you've ever worked on developing smart contracts on the Ethereum blockchain, you're probably familiar with Solidity. It has become the de facto standard for creating decentralized applications (dApps). However, as with any technology, there is no one-size-fits-all solution. This is where Vyper comes in—a programming language designed specifically for writing smart contracts, with an emphasis on simplicity, security, and readability.

Vyper is a high-level programming language intended for use with the Ethereum Virtual Machine (EVM), much like Solidity. But unlike its "older sibling," Vyper was created with a clear focus on eliminating potential vulnerabilities and reducing code complexity. One of its main features is minimalism: Vyper removes many syntax elements and language constructs that could lead to errors or unsafe behavior.

One of the first aspects that sets Vyper apart from other smart contract development languages is its strict typing and the absence of complex structures such as while loops or function modifiers. This is intentional: such constructs often become sources of logical errors or lead to excessive resource consumption during contract execution. The Vyper developers believe that the simpler the code, the lower the chance of errors.

Another important characteristic of Vyper is security. The language is designed to minimize the risk of attacks such as integer overflows or reentrancy attacks. For example, all integers in Vyper are automatically checked for overflow, eliminating the need for additional checks by the developer.

When it comes to code readability, Vyper also has its advantages. Due to a limited set of features and more concise syntax compared to Solidity, reading and understanding smart contracts written in Vyper becomes much easier, even for those without deep programming knowledge. This is particularly important in an open-source environment: third-party auditors can spot errors more quickly and assess the reliability of your contract.

To compare with Solidity, consider a few key points:

• Solidity offers more opportunities for performance optimization through complex constructs. Vyper, on the other hand, prioritizes security.
• Code in Solidity can be less predictable because of features like inline assembly. In Vyper, using low-level code is prohibited.
• Readability in Solidity often suffers due to an abundance of syntactical constructs, while the "less is more" approach in Vyper makes the code more accessible to a wider range of specialists.

Ultimately, the choice between the two languages depends on your goals: if you need full control over the contract and high performance, you might prefer sticking with the familiar Solidity. However, if your key priorities are ease of project maintenance and user security, Vyper is worth considering.

These features make Vyper an ideal choice for cases where you need to write a reliable contract with a minimal number of bugs. What's the next step? Dive deeper into the language's structure!

Before you start writing your first smart contracts in Vyper, you need to set up your workspace. Despite Vyper’s minimalist design, the installation and environment configuration process can raise questions for beginners. Don’t worry—a step-by-step guide is provided below to help you navigate this process quickly.

First Things First: Vyper is written in Python. This means you'll need Python 3.6 or higher installed on your machine (and let's not even try using Python 2.x—it's long been out of date). Additionally, you'll want tools like pip for dependency management and a comfortable IDE (such as Visual Studio Code or PyCharm) to make coding painless.

Step 1: Install Python

If you haven’t installed Python yet:

1. Visit the official Python website.
2. Download the latest stable version.
3. During installation, be sure to check the box that says “Add Python to PATH.” This prevents unnecessary setup headaches later.

To confirm Python installed correctly, run one of these commands in your terminal:

python --version

or

python3 --version

Step 2: Create a Virtual Environment

To avoid dependency conflicts between projects (a common headache), create an isolated virtual environment:

python -m venv vyper_env

Activate the virtual environment:

• On Linux/MacOS:

  source vyper_env/bin/activate
  

• On Windows:

  vyper_env\Scripts\activate.bat
  

Once activated, your terminal prompt will show a (vyper_env) prefix, indicating that you’re working within an isolated space.

Step 3: Install Vyper with pip

Now it’s time to install the Vyper compiler itself:

pip install vyper

Verify the installation with:

vyper --version

If everything went smoothly, you’ll see the current version of the Vyper compiler displayed.

Step 4: Configure Your Development Environment (IDE)

For comfortable coding, it’s important to set up your IDE correctly. Here’s an example using Visual Studio Code:

1. Download and install Visual Studio Code.
2. Install the “Solidity” extension to support .vy file syntax (yes, it works for Vyper too).
3. Configure the VS Code terminal integration to use your virtual environment (vyper_env) through project settings.

Optionally, connect linters like Flake8 or integrate MyPy for type checking—these tools help catch errors before you even run your code.

Step 5: Test Compiling a Simple Contract

Create a file named HelloWorld.vy with the following content:

# A simple example contract in Vyper

@external
def hello() -> String[20]:
    return "Hello, world!"

Compile it in the terminal with:

vyper HelloWorld.vy

If everything is set up correctly, instead of errors, you’ll see the bytecode for your contract!

With that, your basic setup is complete! Your workspace is now ready for writing smart contracts of any complexity. Next up, we’ll explore creating more complex contracts and testing them in a real blockchain environment—stay tuned!

When it comes to developing smart contracts in Vyper, the key aspects are understanding its syntax and structure. Unlike Solidity, where numerous features can sometimes lead to confusion, Vyper emphasizes minimalism and security. Learning the basics of Vyper is not only the first step to creating contracts but also a way to write clean, readable code.

Let's start with the most fundamental concept: the structure of a contract. A smart contract in Vyper is a .vy file that contains state variable definitions, functions, and events. Here’s a simple example:

# A minimal smart contract example in Vyper

# Define a state variable
greeting: public(String[20])

@deploy
def __init__():
    # Initialize the variable when deploying the contract
    self.greeting = "Hello, world!"

@external
def set_greeting(new_greeting: String[20]):
    # Function to change the state variable's value
    self.greeting = new_greeting

@view
@external
def get_greeting() -> String[20]:
    # Read the current value of greeting without changing the blockchain state (view)
    return self.greeting

State variables are defined outside of functions and are stored directly on the blockchain. In the example above, greeting is a string variable with a fixed size (up to 20 characters). The keyword public automatically creates a getter function for this variable.

Data types in Vyper are strictly typed, for instance:

• uint256: an unsigned integer (non-negative whole number);
• int128: a signed integer (from -2^127 to 2^127 - 1);
• address: a wallet or contract address;
• String[N]: a string of fixed length N.

Strict typing prevents many errors at the compilation stage.

Functions are the primary mechanism for interacting with a smart contract. Each function should be marked with a decorator:

• @external is used for functions that can be called from outside the contract.
• @internal indicates that a function can only be called from within the contract.
• @view means the function does not change the blockchain state.
• @pure guarantees no access to the contract state or global blockchain data (like timestamps).

The constructor function (__init__) is marked with the @deploy decorator and is called once during the contract's deployment.

Events are used to record information about actions in the Ethereum transaction log. They are useful for tracking changes without constantly polling data via getter functions:

# Define a state variable
greeting: public(String[20])

# Event to track changes to the greeting
event GreetingChanged:
    old_greeting: String[20]
    new_greeting: String[20]

@deploy
def __init__():
    # Initialize the variable when deploying the contract
    self.greeting = "Hello, world!"

@external
def set_greeting(new_greeting: String[20]):
    # Record an event in the transaction logs
    log GreetingChanged(self.greeting, new_greeting)
    # Function to change the state variable's value
    self.greeting = new_greeting

@view
@external
def get_greeting() -> String[20]:
    # Read the current value of greeting without changing the blockchain state (view)
    return self.greeting

In this example, each change to the greeting is logged via the log function in the event log.

A few important points about Vyper’s syntax:

• Indentation is crucial! Just like Python, Vyper uses indentation instead of curly braces.
• No while loops. Instead of such loops, it's recommended to use strict conditionals or predetermined iteration limits (e.g., for in range()).
• No low-level functionality. Vyper does not support inline assembly, which enhances security.

Vyper forces you to thoughtfully design every element of your code with its concise and strict constructs. This is especially important when working with users’ money in decentralized applications.

Building your first smart contract in Vyper is like learning to ride a bike: it feels a bit daunting at first, but once you start pedaling (i.e., writing code), everything becomes clearer. Let’s walk through creating a simple contract that will help you grasp the basic components and principles of working with this language.

For our first real example, let’s create a contract that acts as a "simple piggy bank." This contract will allow you to deposit funds to its address and withdraw them when needed. This functionality is closer to real financial transactions than just storing a string.

Here's our first smart contract:

# SimplePiggyBank.vy

# Declare a state variable to store the owner
owner: public(address)

# Event to track deposits
event Deposit:
    sender: address
    amount: uint256

# Event to track withdrawals
event Withdrawal:
    recipient: address
    amount: uint256

@deploy
def __init__():
    """
    Constructor function (called upon deployment).
    Sets the contract's owner.
    """
    self.owner = msg.sender

@external
@payable
def deposit():
    """
    Function to deposit funds into the piggy bank.
    Marked @payable so the sender can attach Ether to the transaction.
    """
    # Log the deposit event
    log Deposit(msg.sender, msg.value)

@external
def withdraw(amount: uint256):
    """
    Function to withdraw funds. Only the contract owner
    can withdraw Ether from the piggy bank.
    
    Arguments:
      - amount: The amount in wei to withdraw.
    """
    # Check access rights
    assert msg.sender == self.owner, "You are not the owner!"
    # Check that the piggy bank has enough funds
    assert self.balance >= amount, "Insufficient contract balance!"

    # Execute the transfer
    send(self.owner, amount)

    # Log the withdrawal event
    log Withdrawal(self.owner, amount)

@view
@external
def get_balance() -> uint256:
    """
    Returns the current balance of the contract.
    Marked @view, so it does not alter the blockchain state.
    """
    return self.balance

Key Differences from the "Greeting Contract":

Handling Ether

• Using the @payable decorator in the deposit function allows the contract to accept Ether.
• The built-in function send is used to transfer funds out.

Access Control

• The statement assert msg.sender == self.owner ensures that only the owner can withdraw funds.

Using the Built-in Variable self.balance

• In Vyper, the current balance of the contract is available via self.balance.
• When withdrawing, we compare the requested amount with the actual balance.

Events

• Events like Deposit and Withdrawal are added for logging actions—this lets you monitor transactions without constantly calling get_balance.

Now you have a basic template! The next step could be adding more events to track changes or even trying to implement a basic ERC20 token... But that’s a discussion for later!

Once your Vyper smart contract is written, it's time to verify it works as expected. The compilation and testing phase isn’t just about checking syntax—it’s a way to ensure the contract performs its intended function correctly. Let’s break down this process step by step.

Compiling the Smart Contract

The first step after writing your contract is to compile it. For Vyper, this means converting your human-readable code into bytecode that the Ethereum Virtual Machine (EVM) can execute. To do this, you’ll use the built-in vyper tool you installed earlier.

Suppose you have a file called SimplePiggyBank.vy:

vyper SimplePiggyBank.vy

If there are no errors, the result will be the contract’s bytecode printed to your console. However, for future use, you typically want to save this code to a file. You can do this with the -o flag:

vyper -f abi,bytecode -o ./compiled/SimplePiggyBank.json SimplePiggyBank.vy

This command saves the compiled contract in the compiled folder as a JSON file, containing both the bytecode and the ABI (Application Binary Interface).

Additional ABI Checks

The ABI is crucial for interacting with the contract through applications like dApps or tools such as web interfaces. To get just the ABI of your contract separately:

vyper -f abi -o ./compiled/SimplePiggyBank_abi.json SimplePiggyBank.vy

If you only need the bytecode:

vyper -f bytecode -o ./compiled/SimplePiggyBank_bytecode.json SimplePiggyBank.vy

Now you have all the necessary data: both the bytecode and the ABI.

Simple compilation isn’t enough—it’s important to make sure your contract works as intended. There are several popular tools for testing Vyper contracts, including Brownie and Remix.

Brownie is a Python framework for developing and testing smart contracts. It’s ideal for working with Vyper thanks to its seamless integration with Python, providing powerful tools for local development, testing, and deployment of contracts.

Installing Brownie

Make sure your virtual environment (venv) is activated, then install Brownie:

pip install eth-brownie

Setting Up Your Project

Assume your project has the following structure:

my_vyper_project/
  ├─ contracts/
  │   └─ SimplePiggyBank.vy
  ├─ tests/
  │   └─ test_SimplePiggyBank.py
  ├─ scripts/
  │   └─ deploy.py
  ├─ compiled/
  │   └─ ...
  └─ brownie-config.yaml

While we haven’t detailed brownie-config.yaml before, it’s useful going forward. For example:

networks:
  default: development
  development:
    host: http://127.0.0.1
    port: 8545
    cmd: ganache --server.port=8545 --chain.chainId=1337 --miner.blockTime=1 --logging.debug
    timeout: 120

    gas_price: 10 gwei
    gas_limit: auto

Initialize a new project with Brownie:

brownie init --force

Compiling the Contract

Specify the compiler version at the top of your contract file, for example:

# @version ^0.4.0

You can check your Vyper version with:

vyper --version

It should return something like:

0.4.0+commit.e9db8d9

Before deploying, ensure your contract compiles:

brownie compile

Local Development and Deployment

For local testing, use Ganache—a local blockchain simulator. If you haven’t installed it yet:

npm install -g ganache

Start Ganache in your terminal:

ganache

Now, create a deployment script in scripts/deploy.py:

from brownie import accounts, SimplePiggyBank

def main():
    # Use the first account from the local network
    deployer = accounts[0]

    # Deploy the contract
    piggy_bank = SimplePiggyBank.deploy({"from": deployer})

    print(f"Contract deployed at: {piggy_bank.address}")

Run the deployment script with:

brownie run scripts/deploy.py --network development

Writing Tests

Brownie uses pytest for testing. Create a file tests/test_piggy_bank.py and add the following tests:

import pytest

def test_initial_owner(accounts, SimplePiggyBank):
    piggy_bank = SimplePiggyBank.deploy({'from': accounts[0]})
    assert piggy_bank.owner() == accounts[0]

def test_deposit_and_withdraw(accounts, SimplePiggyBank):
    piggy_bank = SimplePiggyBank.deploy({'from': accounts[0]})

    # Make a deposit of 1 ether
    deposit_tx = piggy_bank.deposit({'from': accounts[1], 'value': "1 ether"})
    deposit_tx.wait(1)

    assert piggy_bank.get_balance() == "1 ether"

    # Attempt to withdraw funds by non-owner
    with pytest.raises(Exception):
        piggy_bank.withdraw("1 ether", {'from': accounts[1]})

    # Owner withdraws funds
    withdraw_tx = piggy_bank.withdraw("1 ether", {'from': accounts[0]})
    withdraw_tx.wait(1)

    assert piggy_bank.get_balance() == 0

Run the tests:

brownie test

Recommendations for Local Development

Working with a Local Network:

• Ganache simulates the Ethereum network. You can add test accounts, execute transactions, and check balances.
• Brownie automatically connects to Ganache if the local network is active.

No Need for Web3 Registration:

• The local network is entirely self-contained. You don’t need to sign up for Infura or other services for development and testing.

Ease of Deployment:

• All operations are local, simplifying debugging and experimentation.

Using Brownie and Ganache, you can develop, test, and debug smart contracts completely locally without registering with Web3 services. It’s a convenient and fast way to master smart contract development and ensure their proper functionality before deploying them on a live network.

Deploying a smart contract on the Ethereum network is the next step after writing and testing your code. We'll use the web3.py library, which offers a convenient interface for interacting with the Ethereum blockchain.

Preparing the Environment

First, make sure you have all necessary tools installed:

1. Create and activate a virtual environment (venv) if you haven't already.

2. Install web3.py:

   pip install web3
   

3. Prepare your compiled contract: you'll need the bytecode and ABI obtained during compilation with Vyper.
4. You’ll also need access to an Ethereum node:
   • For local testing, use Ganache.
   • For working with a public test network (like Ropsten), use a provider such as Infura (registration instructions here).

Deployment Structure

1. Import Dependencies

Create a file called deploy_contract.py and start by importing the necessary modules:

from web3 import Web3
import json

2. Setting Up a Connection to a Node

Specify the URL of your Ethereum node.

• If using Ganache:

  w3 = Web3(Web3.HTTPProvider("http://127.0.0.1:8545"))
  

• To connect via Infura for Ropsten, replace <YOUR_INFURA_PROJECT_ID> with your Infura project ID:

  w3 = Web3(Web3.HTTPProvider("https://ropsten.infura.io/v3/<YOUR_INFURA_PROJECT_ID>"))
  

Check the connection with:

if w3.is_connected():
    print("Connection successful!")
else:
    raise Exception("Failed to connect to the node.")

3. Setting Up an Account for Transactions

To deploy the contract, you need an account with funds (ETH). With Ganache, you can use one of the automatically generated keys. From the Ganache log (displayed on startup), note one of the test accounts and its private key. For example, use the first one:

private_key = "YOUR_PRIVATE_KEY"
deployer_address = "YOUR_ETHEREUM_ADDRESS"

# Optionally check account balance
balance = w3.eth.get_balance(deployer_address)
print(f"Balance: {w3.from_wei(balance, 'ether')} ETH")

4. Loading the ABI and Bytecode

Load the previously created ABI and bytecode files:

with open('compiled/SimplePiggyBank_abi.json', 'r') as abi_file:
    contract_abi = json.load(abi_file)

with open('compiled/SimplePiggyBank_byte.json', 'r') as bytecode_file:
    contract_bytecode = bytecode_file.read().strip()

Now you have everything needed to create a contract instance.

Deploying the Smart Contract

Proceed with deploying the contract as follows:

1. Create a Contract Object Using the ABI:

Contract = w3.eth.contract(abi=contract_abi, bytecode=contract_bytecode)

2. Generate a Deployment Transaction:

using_ganache = True
transaction = Contract.constructor().build_transaction({
    "chainId": 1337 if using_ganache else 3,  # Chain ID: Ganache (1337), Ropsten (3)
    "gas": 3000000,
    "gasPrice": w3.to_wei('10', 'gwei'),  # typical gasPrice for a local network
    "nonce": w3.eth.get_transaction_count(deployer_address),
})

Note: Always verify the current Chain ID of your network!

Signing the Transaction

1. Before sending the transaction to the network, sign it with your private key:

signed_txn = w3.eth.account.sign_transaction(transaction, private_key)
txn_hash = w3.eth.send_raw_transaction(signed_txn.rawTransaction)

print(f"Transaction sent! Transaction hash: {txn_hash.hex()}")

2. After sending, wait for confirmation:

txn_receipt = w3.eth.wait_for_transaction_receipt(txn_hash)
print(f"Contract deployed at address: {txn_receipt.contractAddress}")

You can use the new contract address for further interactions via API functions or dApps.

Now your contract is successfully loaded onto the blockchain! You've just completed the journey from writing a simple Vyper smart contract to deploying it on the blockchain network.

The next step might be implementing the client-side application or integrating interactive functions through a user interface... but that's a story for another time!

When it comes to creating tokens on the Ethereum blockchain, the ERC-20 and ERC-721 standards form the foundation of most applications. They ensure compatibility between smart contracts and make it easy to integrate tokens into ecosystems of wallets, exchanges, and other dApps. Vyper is well-suited for implementing these standards due to its simplicity, strict typing, and focus on security. Let’s explore how to create such tokens using Vyper.

Creating an ERC-20 Token

The ERC-20 standard defines an interface for fungible tokens, like cryptocurrencies or utility tokens. It specifies a minimal set of functions—such as transfer, approve, transferFrom, etc.—as well as events like Transfer and Approval.

interfaces/ERC20.vyi

# @version ^0.4.0

interface ERC20:
    def totalSupply() -> uint256: view
    def balanceOf(owner: address) -> uint256: view
    def allowance(owner: address, spender: address) -> uint256: view
    def transfer(to: address, amount: uint256) -> bool: nonpayable
    def approve(spender: address, amount: uint256) -> bool: nonpayable
    def transferFrom(from_: address, to: address, amount: uint256) -> bool: nonpayable

contracts/ERC20.vy

# Example ERC-20 contract in Vyper
# @version ^0.4.0

from interfaces import ERC20

implements: ERC20

name: public(String[32])
symbol: public(String[10])
decimals: public(uint256)
total_supply: public(uint256)

balances: HashMap[address, uint256]
allowances: HashMap[address, HashMap[address, uint256]]

@deploy
def __init__(initial_supply: uint256):
    self.name = "MyToken"
    self.symbol = "MTK"
    self.decimals = 18
    self.total_supply = initial_supply * 10**self.decimals
    self.balances[msg.sender] = self.total_supply

@view
@external
def balanceOf(account: address) -> uint256:
    return self.balances[account]

@external
def transfer(recipient: address, amount: uint256) -> bool:
    assert self.balances[msg.sender] >= amount, "Insufficient funds"
    self.balances[msg.sender] -= amount
    self.balances[recipient] += amount
    log Transfer(msg.sender, recipient, amount)
    return True

@external
def approve(spender: address, amount: uint256) -> bool:
    self.allowances[msg.sender][spender] = amount
    log Approval(msg.sender, spender, amount)
    return True

@view
@external
def allowance(owner_: address, spender_: address) -> uint256:
    return self.allowances[owner_][spender_]

@external
def transferFrom(sender: address, recipient: address, amount: uint256) -> bool:
    allowed_amount: uint256 = self.allowances[sender][msg.sender]
    assert allowed_amount >= amount and self.balances[sender] >= amount, "Insufficient funds or exceeded authorization"
    self.allowances[sender][msg.sender] -= amount
    self.balances[sender] -= amount
    self.balances[recipient] += amount
    log Transfer(sender, recipient, amount)
    return True

event Transfer:
    sender_indexed: indexed(address)
    receiver_indexed: indexed(address)
    value: uint256

event Approval:
    owner_indexed: indexed(address)
    spender_indexed: indexed(address)
    value: uint256

Creating an ERC-721 (NFT)

ERC-721 is designed for non-fungible tokens (NFTs). These tokens are often used in gaming (e.g., collectible items), art (NFT artworks), or even real estate.

interfaces/ERC721.vyi

# @version ^0.4.0

interface ERC721:
    def balanceOf(owner: address) -> uint256: view
    def ownerOf(tokenId: uint256) -> address: view
    def safeTransferFrom(from_: address, to: address, tokenId: uint256): nonpayable
    def transferFrom(from_: address, to: address, tokenId: uint256): nonpayable
    def approve(to: address, tokenId: uint256): nonpayable
    def setApprovalForAll(operator: address, approved: bool): nonpayable
    def getApproved(tokenId: uint256) -> address: view
    def isApprovedForAll(owner: address, operator: address) -> bool: view

contracts/ERC721.vy

# Example ERC-721 contract in Vyper
# @version ^0.4.0

from interfaces import ERC721

implements: ERC721

NULL_ADDRESS: constant(address) = 0x0000000000000000000000000000000000000000

name: public(String[32])
symbol: public(String[10])

# Mapping from token ID to owner
owners: HashMap[uint256, address]
# Mapping from owner to number of owned tokens
balances: HashMap[address, uint256]
# Mapping from token ID to approved address
token_approvals: HashMap[uint256, address]
# Mapping for operator approvals
operator_approvals: HashMap[address, HashMap[address, bool]]

event Transfer:
    sender_indexed: indexed(address)
    receiver_indexed: indexed(address)
    tokenId: uint256

event Approval:
    owner_indexed: indexed(address)
    approved_indexed: indexed(address)
    tokenId: uint256

event ApprovalForAll:
    owner_indexed: indexed(address)
    operator_indexed: indexed(address)
    approved: bool

@deploy
def __init__():
    self.name = "MyNFT"
    self.symbol = "MNFT"

@view
@external
def balanceOf(owner: address) -> uint256:
    assert owner != NULL_ADDRESS, "The address cannot be null"
    return self.balances[owner]

@view
@external
def ownerOf(tokenId: uint256) -> address:
    owner: address = self.owners[tokenId]
    assert owner != NULL_ADDRESS, "The token doesn't exist"
    return owner

@external
def approve(to: address, tokenId: uint256):
    owner: address = self.owners[tokenId]
    assert to != owner, "You can't approve yourself"
    assert msg.sender == owner or self.operator_approvals[owner][msg.sender], "No permit"

    self.token_approvals[tokenId] = to
    log Approval(owner, to, tokenId)

@view
@external
def getApproved(tokenId: uint256) -> address:
    assert self.owners[tokenId] != NULL_ADDRESS, "The token doesn't exist"
    return self.token_approvals[tokenId]

@external
def setApprovalForAll(operator: address, approved: bool):
    assert operator != msg.sender, "You cannot set a permission for yourself"
    self.operator_approvals[msg.sender][operator] = approved
    log ApprovalForAll(msg.sender, operator, approved)

@view
@external
def isApprovedForAll(owner: address, operator: address) -> bool:
    return self.operator_approvals[owner][operator]

@external
def transferFrom(from_: address, to: address, tokenId: uint256):
    assert to != NULL_ADDRESS, "The recipient cannot be a null address"
    owner: address = self.owners[tokenId]
    assert owner == from_, "The sender is not the owner"
    assert msg.sender == owner or self.token_approvals[tokenId] == msg.sender or self.operator_approvals[owner][msg.sender], "No authorization for transfer"

    # Reset approvals
    self.token_approvals[tokenId] = NULL_ADDRESS

    # Update balances
    self.balances[from_] -= 1
    self.balances[to] += 1

    # Change token owner
    self.owners[tokenId] = to

    log Transfer(from_, to, tokenId)

@external
def mint(to: address, tokenId: uint256):
    assert to != NULL_ADDRESS, "The address cannot be null"
    assert self.owners[tokenId] == NULL_ADDRESS, "The token already exists"

    self.balances[to] += 1
    self.owners[tokenId] = to

    log Transfer(NULL_ADDRESS, to, tokenId)

@external
def burn(tokenId: uint256):
    owner: address = self.owners[tokenId]
    assert owner == msg.sender, "Only the owner can burn the token"

    # Update balances and remove ownership
    self.balances[owner] -= 1
    self.owners[tokenId] = NULL_ADDRESS

    log Transfer(owner, NULL_ADDRESS, tokenId)

Implementation Features in Vyper:

Simplicity and Security:

• The contract minimizes the number of functions while adhering to the ERC-721 standard.
• Strict typing prevents overflow errors and misuse of data.

Events (Logs):

• The Transfer, Approval, and ApprovalForAll events allow tracking of token transfers and changes in permissions.

Permission Mechanism:

• Both individual (approve) and global (setApprovalForAll) permissions are supported for managing tokens.

Mint Function:

• Allows creation of new tokens, assigning them to an owner.
• Ensures the token ID is unique.

Burn Function:

• Allows the owner to destroy a token.

Compatibility:

• The implementation fully complies with the ERC-721 interface, enabling easy integration of tokens into the existing ecosystem.

The advanced features of Vyper make it an ideal tool for writing secure and optimized smart contracts. Its minimalist design is not only aesthetically pleasing but also eliminates a wide range of potential vulnerabilities common in more complex languages like Solidity. However, even with such a strict language, it's important to know best practices for writing quality code to enhance the reliability and efficiency of your contracts.

Security Principles in Vyper:

1. Avoid Numeric Overflows

One of the most common attacks on smart contracts involves integer overflows or underflows. Unlike Solidity before version 0.8.x—where developers had to manually use libraries like SafeMath—Vyper prevents such errors automatically: the language checks value boundaries on its own.

@external
def safe_addition(a: uint256, b: uint256) -> uint256:
    return a + b  # Automatically checks for overflow

An attempt to exceed allowable values will cause a compilation or runtime error without the need for additional libraries.

2. Access Control

Managing permissions is a crucial part of any logic. Use explicit checks for owners or authorized users:

owner: public(address)

@external
def __init__():
    self.owner = msg.sender

@external
def restricted_function():
    assert msg.sender == self.owner, "Access denied"

This simple construct helps avoid unauthorized access issues.

3. Preventing Reentrancy Attacks

Reentrancy attacks are among the most notorious threats to Ethereum smart contracts (remember the DAO hack). Vyper reduces the likelihood of such attacks by eliminating function modifiers and low-level calls (call), which malicious actors might exploit.

Optimizing Smart Contracts in Vyper:

Vyper emphasizes readability and minimalism, which inherently aids optimization. Still, here are a few additional recommendations:

1. Use Fixed-Size Data Types

Blockchain memory is expensive (literally), so using fixed data types can significantly lower gas costs:

• Use bytes[N] instead of String if the string length is known in advance.

• For arrays, try to specify a maximum length when declaring:

  data: bytes[32]
  numbers: uint256[10]
  

  This simplifies the compiler's job and reduces operational costs.

2. Minimize Loops

Although Vyper supports for loops with strict iteration limits (infinite loops are not allowed), they can quickly raise transaction costs with a large number of elements.

It’s better to avoid long lists within the contract; instead, store data off-chain or break tasks into several transactions.

3. Use Events Instead of Storing Data

For temporary information, use events rather than state variables to save on gas:

event DataStored:
    user_indexed: indexed(address)
    value: uint256

@external 
def log_data(value: uint256):
    log DataStored(msg.sender, value)

Events are cheaper than writing to blockchain storage and are useful for tracking history without bloating the contract size.

Additional Tips

• Always test your contracts using frameworks like Brownie or Pytest.
• Audit your code before deploying, even on test networks.
• Document every function! Clear comments make your project easier to understand for other developers or auditors.

• Be cautious with "magic numbers." It’s better to define them as constants:

  MAX_SUPPLY: constant(uint256) = 1000000
  

Vyper code should be as simple as possible—this is how you achieve the security and reliability of your dApp! By following these principles, you'll be able to create an efficient contract without unnecessary risks to users (and without stressing yourself out).

The practical application of Vyper in real projects showcases its potential as an excellent tool for creating secure and efficient smart contracts. Although Solidity remains the more popular choice among Ethereum developers, Vyper is actively used in projects where prioritizing security, readability, and minimizing the attack surface is essential.

One standout example is Vyper’s use in decentralized finance (DeFi) applications. For instance, projects like Curve Finance have chosen this language due to its focus on security. Curve is an automated market maker (AMM) protocol that optimizes the exchange of stable assets with minimal fees. Curve’s developers claim that Vyper’s strict typing and simplified syntax helped avoid numerous potential vulnerabilities during contract development. Utilizing Vyper allowed the project to set new reliability standards in the DeFi sector.

Another successful application is Synthetix, a platform for trading blockchain-based derivatives on Ethereum. Key components of the Synthetix system were rewritten using Vyper specifically to ensure maximum transparency in contract logic and to prevent errors arising from complex code structures.

In the NFT (non-fungible token) space, projects also leverage Vyper’s capabilities. For example, smaller collectible platforms use this language to create smart contracts with straightforward token issuance logic and owner rights management. This is particularly relevant given the NFT industry's growth: the simplicity of contract audits becomes critically important for building user trust.

At the institutional level, Vyper is often chosen for implementing DAOs (Decentralized Autonomous Organizations). Strict access control to functions and the limitation of low-level logic make it an ideal candidate for writing voting contracts or fund distribution mechanisms within a DAO.

The prospects for using Vyper extend far beyond current applications. As more companies and developers focus on the security of their solutions on the Ethereum blockchain, Vyper’s popularity continues to grow. In the long term, it could become the de facto standard where increased confidence in contract correctness is required—such as in government voting systems or corporate supply chain management.

Vyper has firmly established itself as a programming language focused on security and minimalism within the Ethereum ecosystem. Its simplicity and strict typing make it an attractive choice for projects where errors can cost millions of dollars or undermine user trust. In the long run, Vyper is well-positioned to become a key tool for developing highly reliable smart contracts, especially in critical areas like decentralized finance (DeFi), DAO governance, and asset tokenization.

Despite Solidity’s current dominance, the growing emphasis on contract security is encouraging developers to explore alternatives. Vyper has already gained popularity among teams with high accountability—for example, Curve Finance has demonstrated the language’s viability in real-world conditions. This precedent shows that projects handling billions in liquidity are willing to choose less "popular" tools for the sake of reliability.

Vyper’s prospects are further strengthened by Ethereum’s own development. With the network’s transition to Proof of Stake (PoS) and the implementation of upgrades like sharding and rollups, the demand for secure contracts is only set to increase. Moreover, the reduction in gas costs following the implementation of EIP-1559 opens up new opportunities for using Vyper’s optimized code even with more complex logic.

Another growth factor is the increasing focus on blockchain’s regulatory aspects. Companies are seeking solutions with guaranteed transparency and minimized risks. Here, Vyper’s concise syntax becomes an advantage over competitors by simplifying contract audits.

However, challenges remain: the development ecosystem around Vyper is not as mature compared to Solidity. Increasing the number of libraries and testing tools will be a crucial step forward in attracting more developers.

In the future, Vyper’s role could expand beyond traditional dApps:

• Government Applications: Voting systems or fund distribution mechanisms.
• Corporate Networks: Supply chain management or financial operations automation.
• NFT 2.0: Creating new standards for non-fungible tokens with enhanced ownership security requirements.

Although the path ahead will be challenging due to competition from other languages (such as Rust through Substrate in Polkadot), Ethereum’s focus on versatility provides a solid foundation for Vyper’s continued growth.

Thus, the future of Vyper looks promising: it is capable of occupying a significant niche where the risk of errors is unacceptable—whether it’s protecting user funds or managing global processes through decentralized technologies.