This contract is for creating a sample funding contract written in Vyper.

buy_me_a_coffee.vy

# pragma version 0.4.0
"""
@license MIT
@title Buy Me A Coffee!
@author Me
@notice This contract is for creating a sample funding contract
"""

# sepolia testnet chainlink eth / usd: 0x694AA1769357215DE4FAC081bf1f309aDC325306


# We'll learn a new way to do this later...
interface AggregatorV3Interface:
    def decimals() -> uint8: view
    def description() -> String[1000]: view
    def version() -> uint256: view
    def latestAnswer() -> int256: view

# Constants & Immutables
MINIMUM_USD: public(constant(uint256)) = as_wei_value(5, "ether")
PRICE_FEED: public(immutable(AggregatorV3Interface)) 
OWNER: public(immutable(address))
PRICISION: constant(uint256) = 1 * (10 ** 18)

# Storage
funders: public(DynArray[address, 1000])
funders_to_amount_funded: public(HashMap[address, uint256])

# With constants: 262, 853
@deploy
def __init__(price_feed: address):
    PRICE_FEED = AggregatorV3Interface(price_feed)
    OWNER = msg.sender

@external
@payable
def fund():
    self._fund()


@internal
@payable
def _fund():
    """Allows users to send $ to this contract
    Have a minimum & amount to send

    How do we convert the ETH amount to dollars amount? 
    """
    usd_value_of_eth: uint256 = self._get_eth_to_usd_rate(msg.value)
    assert usd_value_of_eth >= MINIMUM_USD, "You must spend more ETH than 5 dollar"
    self.funders.append(msg.sender)
    self.funders_to_amount_funded[msg.sender] += msg.value


@external
def withdraw():
    """
    Take the money out of the contract, that people sent via the fund function.
    How do we make sure only we can pull the money out? 
    """
    assert msg.sender == OWNER, "Not the owner of the contract! "
    raw_call(OWNER, b"", value = self.balance)
    # send(OWNER, self.balance)
    # resetting
    for funder: address in self.funders:
        self.funders_to_amount_funded[funder] = 0
    self.funders = []

@internal
@view
def _get_eth_to_usd_rate(eth_amount: uint256) -> uint256:
    """
    Chris sent us 0.01 ETH for us to buy a coffee
    Is that more or less than $5?
    """
    price: int256 = staticcall PRICE_FEED.latestAnswer()
    eth_price: uint256 = (convert(price, uint256)) * (10 ** 10)
    eth_amount_in_usd: uint256 = (eth_price * eth_amount) // PRICISION
    return eth_amount_in_usd

@external
@view 
def get_eth_to_usd_rate(eth_amount: uint256) -> uint256:
    return self._get_eth_to_usd_rate(eth_amount)


@external 
@payable 
def __default__():
    self._fund()

vyper_sample.vy

# SPDX-License-Identifier: MIT
# pragma 和版本说明
# Vyper版本必须指定，不能有浮动范围
# 这是因为Vyper的安全性和语法更新比较频繁

@version ^0.4.0

# 状态变量的声明
# 状态变量会永久存储在以太坊区块链上
owner: public(address)
balance: public(uint256)
is_active: public(bool)
user_data: public(map(address, uint256))

# 事件定义
# 事件用于在区块链上记录信息，以便前端或外部观察器监听
# 这里定义了一个转账事件

Transfer: event({recipient: address, amount: uint256})

# 构造函数
# @external 和 @payable 关键字的使用
# @external 表示这个函数可以从合约外部调用
# @payable 表示这个函数可以接收以太币

@external
@payable
def __init__():
    # msg.sender 表示调用该合约的地址
    self.owner = msg.sender
    self.balance = msg.value
    self.is_active = True

# 修改器的实现 (Vyper中没有modifier，使用内联的require实现)
# 这里用一个内联require来检查只有owner才能调用

@external
def set_active(active: bool):
    assert msg.sender == self.owner, "Only owner can change status"
    self.is_active = active

# 发送以太币
# @payable 标识允许接收以太币
# emit 用于触发事件

@external
@payable
def deposit():
    self.balance += msg.value
    log Transfer(msg.sender, msg.value)

# 提款功能
# 处理ETH转账以及安全性检查

@external
def withdraw(amount: uint256):
    assert msg.sender == self.owner, "Only owner can withdraw"
    assert amount <= self.balance, "Insufficient balance"
    self.balance -= amount
    send(msg.sender, amount)

# 更新用户数据 (映射操作)
@external
def update_user_data(user: address, data: uint256):
    self.user_data[user] = data

# 读取用户数据
# view修饰符表示这个函数不会修改区块链上的数据

@external
@view
def get_user_data(user: address) -> uint256:
    return self.user_data[user]

# 删除合约的函数已在 Vyper 0.4.0 中移除，因此不再使用 selfdestruct

# 主要的Vyper语言特性：
# 1. 状态变量: `owner`, `balance`, `is_active`, `user_data`
# 2. 数据类型: `address`, `uint256`, `bool`, `map`
# 3. 事件: `Transfer`
# 4. 修饰符 (通过assert实现)
# 5. 构造函数: `__init__`
# 6. 以太币传输: `send`, `msg.value`
# 7. 可见性修饰符: `@public`, `@external`, `@view`, `@payable`
# 8. 映射: `map`
# 9. 断言: `assert`
# 10. 删除了 selfdestruct