Environment Variables and Constants¶

Environment Variables¶

Environment variables always exist in the namespace and are primarily used to provide information about the blockchain or current transaction.

Block and Transaction Properties¶

Name	Type	Value
`block.coinbase`	`address`	Current block miner’s address
`block.difficulty`	`uint256`	Current block difficulty
`block.prevrandao`	`bytes32`	Current randomness beacon provided by the beacon chain
`block.number`	`uint256`	Current block number
`block.gaslimit`	`uint256`	Current block’s gas limit
`block.basefee`	`uint256`	Current block’s base fee
`block.blobbasefee`	`uint256`	Current block’s blob gas base fee
`block.prevhash`	`bytes32`	Equivalent to `blockhash(block.number - 1)`
`block.timestamp`	`uint256`	Current block epoch timestamp
`chain.id`	`uint256`	Chain ID
`msg.data`	`Bytes`	Message data
`msg.gas`	`uint256`	Remaining gas
`msg.sender`	`address`	Sender of the message (current call)
`msg.value`	`uint256`	Number of wei sent with the message
`tx.origin`	`address`	Sender of the transaction (full call chain)
`tx.gasprice`	`uint256`	Gas price of current transaction in wei

Note

block.prevrandao is an alias for the block.difficulty opcode. Since block.difficulty is considered deprecated according to EIP-4399 after “The Merge” (Paris hard fork), we recommend using block.prevrandao.

Note

msg.data requires the usage of slice to explicitly extract a section of calldata. If the extracted section exceeds the bounds of calldata, this will throw. You can check the size of msg.data using len.

The self Variable¶

self is an environment variable used to reference a contract from within itself. Along with the normal address members, self allows you to read and write to state variables and to call private functions within the contract.

Name	Type	Value
`self`	`address`	Current contract’s address
`self.balance`	`uint256`	Current contract’s balance

Accessing State Variables¶

self is used to access a contract’s state variables, as shown in the following example:

state_var: uint256

@external
def set_var(value: uint256) -> bool:
    self.state_var = value
    return True

@external
@view
def get_var() -> uint256:
    return self.state_var

Calling Internal Functions¶

self is also used to call internal functions within a contract:

@internal
def _times_two(amount: uint256) -> uint256:
    return amount * 2

@external
def calculate(amount: uint256) -> uint256:
    return self._times_two(amount)

Custom Constants¶

Custom constants can be defined at a global level in Vyper. To define a constant, make use of the constant keyword.

TOTAL_SUPPLY: constant(uint256) = 10000000
total_supply: public(uint256)

@deploy
def __init__():
    self.total_supply = TOTAL_SUPPLY