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.. index:: type

Constants and Environment Variables

Built In Constants

Vyper has a few convenience constants builtin.

Name Type Value
ZERO_ADDRESS address 0x0000000000000000000000000000000000000000
EMPTY_BYTES32 bytes32 0x0000000000000000000000000000000000000000000000000000000000000000
MAX_INT128 int128 2**127 - 1
MIN_INT128 int128 -2**127
MAX_DECIMAL decimal (2**127 - 1)
MIN_DECIMAL decimal (-2**127)
MAX_UINT256 uint256 2**256 - 1
ZERO_WEI uint256(wei) 0

Custom Constants

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

Example:

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

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

Advanced Example:

units: {
    share: "Share unit"
}

MAX_SHARES: constant(uint256(share)) = 1000
SHARE_PRICE: constant(uint256(wei/share)) = 5

@public
def market_cap() -> uint256(wei):
    return MAX_SHARES * SHARE_PRICE

Environment Variables

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

Note

msg.sender and msg.value can only be accessed from public functions. If you require these values within a private function they must be passed as parameters.

Name Type Value
block.coinbase address Current block miner’s address
block.difficulty uint256 Current block difficulty
block.number uint256 Current block number
block.prevhash bytes32 Equivalent to blockhash(block.number - 1)
block.timestamp uint256 Current block epoch timestamp
msg.gas uint256 Remaining gas
msg.sender address Sender of the message (current call)
msg.value uint256(wei) Number of wei sent with the message
tx.origin address Sender of the transaction (full call chain)
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