This lesson focuses on adding a minting function to the original ERC20 token so our new minter has something to call.

The lesson covers how to access state variables and a few basic Vyper variable types.

State variables are data contained in your contract. Users spend gas to write or modify their values. They are declared outside of functions, along with their variable type.

my_variable_name : variable_type

State variables are considered to be in the "module" scope of the contract. These variable can be accessed within the scope of "functions" using the self object.

state_var: uint

def foo():
     function_var: uint = self.state_variable

A variable can be added to another variable in Pythonic syntax using the += operator

x : uint = 1
x += 2
# Value of x is now 3

Vyper is a statically typed language. The type of each variable (state and local) must be specified or at least known at compile-time. Vyper provides several elementary types which can be combined to form complex types.

A variable type that holds an Ethereum address. Written as a 20 or 160 bit checksummed hexadecimal with leading 0x

An unsigned integer (uint) variable can store numerical values 0 through 2 ** N - 1 Default value for N is 256 (uint256) - N can be as low as 8 No decimal places are allowed for integers types

A HashMap is a key-value that loosely resembles a Python dictionary but works quite differently. Unlike a Python dictionary, the key data is not stored in a HashMap, so it's impossible to run loops. They serve as gas-efficient variable type to store large sets of data. HashMaps can point to other HashMaps for multidimensinoal data storage.

balances: HashMap[address, uint]
balances[your_address] = 1000