Lab 3: Deployment and interactions with smart-contracts
=======================================================

In this lab, we are going to interact with out contract from python.

Interacting with our first contract from lab 2
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

In this section, we are going to call our contract from lab 2 directly from python. To do so, we need
two things:
- The contract's address, to now where to call the functions
- A way to know what functions are available and how to call them

The contract ABI
----------------

As it is, your python program has no idea how to call your contract. Especially, what functions are available.

To do so, we need to provide it your contract's *Application Binary Interface* (ABI). You're contract ABI 
is a file that list all available functions and what parameters you need to provide. Given a contract ABI,
python is (with the web3 library) available to generate every function calls to your contract, so you 
can easily create a python application that can interact the contract.

To get your contract's ABI, you need to have it compiled first on Remix. Go on the Solidity compiler window,
and click on **ABI** to copy the contract ABI. Paste it in a new file called "ABI.json".

.. tip:: Use version 0.8.0 of the Solidity compiler

.. admonition:: Task

        Try to have a look at this file and try to find where your functions have been defined. 

The contract address
--------------------

Now that we have a way to tell python what functions are in our contract, we need to tell it where to actually
send the transactions. Remember that a contract has an address where you can call it.

To get a contract adress, you need to deploy it first. This should have been done in the previous lab. You
can go on the deployment window and click on your deloyed contract to copy its address.

.. admonition:: Task

        Get the :download:`provided </_static/Lab3.py>` python script for this lab and modify the **CONTRACT_ADDRESS** variable to paste your own contract
        address. Try to run it. It should print the value stored in the **name** variable in your deployed contract. 

.. tip:: If it does not print anything after "It returns:", make sure you have actually called "setName" once.
    You can still do it in Remix.

Complete the script
-------------------

.. admonition:: Task

        Now, try to implement calls to the various functions you have in your contract. 

.. admonition:: Question
    
    Some functions (**setName**, **setCapacity**) needs to be called with **transact()**, some (**getName**, **getCapacity**) needs to be called with 
    **call()**. Can you guess why and what are the differences between those functions?

.. tip:: If you want to make your program a bit more interactive, you can use the "input" python built in function 
    to ask the user for an input while executing the script. This can be nice for the setName and setCapacity functions!

The documentation can be found here: https://web3py.readthedocs.io/en/v5/contracts.html#id3.