A hello world Vyper contract.

hello.sol

pragma solidity 0.5.3; // Solidity version 0.5.3, pragma used to enable certain compiler features or checks

contract HelloWorld // defining the contract
{
    string greeting; // defining the state string variable 'greeting'
    
    constructor() // constructor function, optional, executed once upon deployment and cannot be called again
    public
    {
        greeting = "Hello, World.";
    }
    
    function printGreeting() // defining a function
    public // this function is callable by anyone 
    view // dictates that this function promises to not modify the state
    returns (string memory) // function returns a string variable from memory
    {
        return greeting;
    }
    
    function setGreeting(string memory _greeting)
    public 
    // notice that this function contains no "view" -- it modifies the state
    {
        greeting = _greeting;
    }
}

hello.vy

greeting: public(bytes[32]) # defining greeting state variable, just like Solidity

@public
def __init__(): # initialization function, same as Solidity's constructor function
    self.greeting = "Hello, World."
    
@public # function can be called internally and externally
@constant # function will not change state
def printGreeting() -> bytes[32]:
    return self.greeting

@public
def setGreeting(_greeting: bytes[32]): # a state changing function
    self.greeting = _greeting