NRE and scripting

Nile provides an API to build scripts leveraging the Nile Runtime Environment (NRE), an object exposing Nile’s functionality from compilation to account and deployment management. Nile scripts implement an asynchronous def run(nre) function that receives the NileRuntimeEnvironment object.

Running a script

Create a file named test_script.py inside the scripts/ directory at the root of your project with the following contents. Keep in mind that the scripts/ directory is a suggested convention but not a requirement.
```
async def run(nre):
    accounts = await nre.get_accounts(predeployed=True)
    print("First Account:", accounts[0])
```
The predeployed parameter leverages the accounts that come already deployed with the local node. Read get_accounts’s API Reference to learn more.
Run a devnet node with nile node
```
nile node
```
Run the script by using nile run
```
nile run scripts/test_script.py
```

You can change the script’s target network with the --network option.

For a full reference of NRE exposed members check the NRE Reference section.

Useful Script Examples

In this section you can find some potentially helpful script examples.

Declare the OZ account

Useful if you need to deploy the account in a local devnet node, for previous declaration:

# scripts/declare_oz_account.py
async def run(nre):
  accounts = await nre.get_accounts(predeployed=True)
  declarer_account = accounts[0]

  # nile_account flag tells Nile to use its pre-packed artifact
  #
  # If we don't pass a max_fee, nile will estimate the transaction
  # fee by default. This line is equivalent to:
  #
  # tx = await declarer_account.declare("Account", max_fee=0, nile_account=True)
  # max_fee = await tx.estimate_fee()
  # tx.update_fee(max_fee)
  #
  # Note that tx.update_fee will update tx.hash and tx.max_fee members
  tx = await declarer_account.declare("Account", nile_account=True)

  tx_status, *_ = await tx.execute(watch_mode="track")

  print(tx_status.status, tx_status.error_message or "")

Transfer funds from a predeployed devnet account

Useful for funding addresses in devnet:

# scripts/transfer_funds.py
from nile.common import ETH_TOKEN_ADDRESS
from nile.utils import to_uint, hex_address

async def run(nre):
  accounts = await nre.get_accounts(predeployed=True)
  account = accounts[0]

  # define the recipient address
  recipient = "0x05a0ca51cbc03e5ec8d9fad116f8737a6afe2613b3128ebd515643a1a5e5c52d"

  # define the amount to transfer
  amount = 2 * 10 ** 18

  print(
    f"Transferring {amount} WEI\n"
    f"from {hex_address(account.address)}\n"
    f"to   {recipient}\n"
  )

  # If we don't pass a max_fee, nile will estimate the transaction fee by default
  tx = await account.send(ETH_TOKEN_ADDRESS, "transfer", [recipient, *to_uint(amount)])

  tx_status, *_ = await tx.execute(watch_mode="track")

  print(tx_status.status, tx_status.error_message or "")