Imports

The import statements allow us to import Vyper code using the import or from ... import syntax.

Example of file structure:

├── YourContract.vy
└── HelperContract.vy

HelperContract.vy

# pragma version 0.4.0

@external
@pure
def addition_function(x: uint256, y: uint256) -> uint256:
    return x + y

YourContract.vy

import HelperContract                  # accessed as `HelperContract`

# Alternatives to importing `HelperContract.vy`
# import HelperContract as hc            --> accessed as `hc`
# from . import HelperContract           --> accessed as `HelperContract`
# from . import HelperContract as hc     --> accessed as `ex`

@external
def calculate_sum(x: uint256, y: uint256) -> uint256:
    return HelperContract.addition_function(x, y)

Vyper also includes built-in interfaces such as IERC20 and IERC721 in its language. These can be imported from ethereum.ercs.

from ethereum.ercs import IERC20

implements: IERC20

balance_of_address: public(HashMap[address, uint256])

# Example of `transfer` function accessing `IERC20` interface
@external
def transfer(_to: address, _value: uint256) -> bool:

    self.balanceOf[msg.sender] -= _value
    self.balanceOf[_to] += _value
    log IERC20.Transfer(msg.sender, _to, _value)
    return True

Vyper Differentiators

You can assign alias to the imported contract using as keyword.
Vyper has built-in interfaces

Imports

Further Reading: