Vyper ERC-20 Token

# @version ^0.3.10

name: public(String[32])
symbol: public(String[32])
decimals: public(uint8)
totalSupply: public(uint256)
balanceOf: public(HashMap[address, uint256])
allowance: public(HashMap[address, HashMap[address, uint256]])

@external
def __init__(_name: String[32], _symbol: String[32], _decimals: uint8, _supply: uint256):
    self.name = _name
    self.symbol = _symbol
    self.decimals = _decimals
    self.totalSupply = _supply
    self.balanceOf[msg.sender] = _supply

@external
def transfer(_to: address, _amount: uint256) -> bool:
    assert _to != empty(address)
    self.balanceOf[msg.sender] -= _amount
    self.balanceOf[_to] += _amount
    return True

@external
def approve(_spender: address, _amount: uint256) -> bool:
    self.allowance[msg.sender][_spender] = _amount
    return True