# Aave - Lending and Borrowing
## Objectives
1. Swap some ETH for WETH.
2. Deposit some WETH into Aave.
3. Borrow some asset against the collateral(deposit).
1. Challenge: Sell that borrowed asset (short selling)
4. Repay everything back.
> aave testnet v2 is on kovan: \
> aave testnet v3 is on rinkeby:
### Testing
* Integration test: Kovan (v2) / Rinkeby (v3)
* Unit tests: Mainnet-fork
If you are not working with oracles and don't need to mock off-chain responses, use a mainnet fork to run unit tests.
## Deposit ETH
When you deposit ETH into AAVE, it gets swapped to WEth (ERC20 version of ETH) and then deposited.
{% hint style="info" %}
**Why must we convert to WETH?**
* Aave requires ERC20 properties of tokens for its ecosystem functionality.
* ETH does not conform to ERC-20.
* Wrapping ETH allows you to trade directly with Alt Tokens.
{% endhint %}
You will receive aETH which is the interest bearing token, reflective of your deposit and the interest it accrues.
The Aave deposit function will handle all the necessary conversions from ETH. However, we can save on gas by locking our ETH for WETH directly with the WETHGateway contract.
#### Create get\_weth()
Objective: Get WETH by depositing ETH \[call deposit function on WEth contract].
* To interact with the contract, we need ABI + Address.
* For ABI, use interface, IWEth.sol, from
* create IWeth.sol in interfaces folder -> copy and paste github code into it.
{% tabs %}
{% tab title="get\_weth().py" %}
```python
from brownie import config, network, interface
from scripts.helpful_scripts import get_account
def get_weth():
"""
how to get Weth?
deposit eth to WETH contract, it gives us ETH
https://kovan.etherscan.io/token/0xd0a1e359811322d97991e03f863a0c30c2cf029c#writeContract
to interact with this contract we need: address + ABI
ABI: use interface, IWEth.sol, from https://github.com/PatrickAlphaC/aave_brownie_py_freecode/tree/main/interfaces
create IWeth.sol in interfaces folder -> copy and paste github code into it.
"""
account = get_account()
weth = interface.IWeth(config["networks"][network.show_active()]["weth_token"])
#deposit 0.1 ETH, should get back 0.1 WETH
tx = weth.deposit({"from": account, "value": 0.1 * 10**18})
tx.wait(1)
print("...Received 0.1WETH...")
return tx
def main():
get_weth()
```
{% endtab %}
{% tab title="brownie-config.yaml" %}
```yaml
dotenv: .env
networks:
default: development
rinkeby:
weth_token: '0xc778417E063141139Fce010982780140Aa0cD5Ab' #WEthGateway contract
verify: True
kovan:
weth_token: '0xd0A1E359811322d97991E03f863a0C30C2cF029C' #WEthGateway contract
verify: True
mainnet-fork: #development env, fork uses live mainnet addresses
weth_token: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2' #WEthGateway contract
mainnet: # for production
weth_token: '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2' #WEthGateway contract
wallets:
wallet1: ${PRIVATE_KEY}
```
{% endtab %}
{% tab title="helpful-scripts.py" %}
```python
from brownie import network,accounts,config
LOCAL_BLOCKCHAIN_ENV = ["development", "ganache-local"]
FORKED_LOCAL_ENV = ["mainnet-fork", "mainnet-fork-dev"]
def get_account(index=None,id=None):
# accounts[0] -- ganache accounts
# accounts.add("env") -- private key from env file -> accounts.add(config["wallets"]["wallet1"])
# accounts.load("id") -- load from brownie accounts list
if index:
# if index was passed return ganache account
return accounts[index]
if id:
return accounts.load(id)
if network.show_active() in LOCAL_BLOCKCHAIN_ENV or network.show_active() in FORKED_LOCAL_ENV:
return accounts[0] #use ganache generated account.
else: #look in config.yaml
return accounts.add(config["wallets"]["wallet1"])
```
{% endtab %}
{% endtabs %}
On running get\_weth.py successfully, you should see 0.1 WEth in your Metamask wallet.
{% hint style="info" %}
If you want to convert Weth back to Eth, call the withdraw function. The function will return us the ETH we stored with the contract, on reclaiming the WETH.
{% endhint %}
