Learn VYPER with Real Code Examples

count: public(uint256)

@external
def __init__():
    self.count = 0

@external
def increment():
    self.count += 1

@external
def reset():
    self.count = 0

A minimal counter smart contract using Vyper with increment and reset functions.

owner: public(address)
message: public(String[100])

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

@external
def set_message(new_message: String[100]):
    assert msg.sender == self.owner
    self.message = new_message

A contract where only the owner can update a stored message.

balances: public(HashMap[address, uint256])

@payable
@external
def deposit():
    self.balances[msg.sender] += msg.value

@external
def withdraw(amount: uint256):
    assert self.balances[msg.sender] >= amount
    self.balances[msg.sender] -= amount
    send(msg.sender, amount)

A tiny bank contract allowing users to deposit and withdraw ETH.

total_supply: public(uint256)
balances: public(HashMap[address, uint256])

@external
def __init__(_s: uint256):
    self.total_supply = _s
    self.balances[msg.sender] = _s

@external
def transfer(to: address, amount: uint256):
    assert self.balances[msg.sender] >= amount
    self.balances[msg.sender] -= amount
    self.balances[to] += amount

A simplified ERC20-style token for demonstration purposes.

unlock_time: public(uint256)

@payable
@external
def __init__(_unlock: uint256):
    self.unlock_time = _unlock

@external
def withdraw():
    assert block.timestamp >= self.unlock_time
    send(msg.sender, self.balance)

A simple timelock contract where ETH can only be withdrawn after a specific timestamp.

yes: public(uint256)
no: public(uint256)

@external
def vote(choice: bool):
    if choice:
        self.yes += 1
    else:
        self.no += 1

A tiny voting system with yes/no votes.

owner: public(address)
whitelist: public(HashMap[address, bool])

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

@external
def add_user(user: address):
    assert msg.sender == self.owner
    self.whitelist[user] = True

@external
def restricted_action():
    assert self.whitelist[msg.sender] == True

A contract that allows only whitelisted addresses to perform an action.

event Log:
    creator: address
    message: String[100]

@external
def fire(msg: String[100]):
    log Log(msg.sender, msg)

A simple example of Vyper events.

CONFIG: immutable(uint256)

@external
def __init__(v: uint256):
    CONFIG = v

@external
def get_config() -> uint256:
    return CONFIG

Shows how to use `immutable` variables in Vyper.

factor: public(uint256)

@external
def __init__(_factor: uint256):
    self.factor = _factor

@external
def multiply(x: uint256) -> uint256:
    return x * self.factor

A utility contract that multiplies a number by a constant stored in the contract.