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Lesson 4:
Immutable
Introduction to immutable keyword in Vyper
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Immutable
Immutable variables are similar to constants, except the value must be defined in the constructor of the contract. Declare immutable variables if you want a variable to remain constant throughout the lifetime of a deployed contract.
Accessing an immutable variable reduces runtime gas costs in comparison with constant variables.
# pragma version 0.4.0
IMMUTABLE_INT: immutable(uint256)
IMMUTABLE_ADDR: immutable(address)
@deploy
def __init__():
IMMUTABLE_INT = 999
IMMUTABLE_ADDR = 0xE2b4795039517653c5Ae8C2A9BFdd783b48f447A
@external
@view
def retrieveImmutables() -> (uint256, address):
return (IMMUTABLE_INT, IMMUTABLE_ADDR)Vyper Differentiators
- Immutable variables cannot have any initial values.