Environment variables

There are environment variables that describe the block properties and the transaction. If you want to know which block you are in right now (remember that a smart contract lives in the blockchain), you can retrieve it from block.number. If you are keen to know the number of ethers that a user sends to a smart contract, you can use msg.value. If you are curious to know who sends money, you can query the information from msg.sender. If you want to store the time when a user sends ethers, you can use block.timestamp.

To demonstrate the environment variables, let’s create a Vyper file, named EnvVar.vy, and add the following code to it:

# @version ^0.3.0
donatur: address
donation: uint256
time: uint256
@external
@payable
def donate():
    self.donatur = msg.sender
    self.donation = msg.value
    self.time = block.timestamp

When a user executes the donate function, they can send ethers or...