PyTeal Migration

Classes and Functions

PyTeal	TEALScript
Txn	this.txn
Global	globals
Itxn	this.itxn
Assert	assert
NamedTuple	See Objects section here
Gtxn	this.txnGroup
precompile	See multiple contracts

Maybe Values

In TEALScript, there is no concept of MaybeValue. For every opcode that would return a MaybeValue in PyTeal, TEALScript exposes two methods. One to get the value and one to get whether the value exists. Simply getting the value will always assert that the value exists. For boxes, the means needing to call exist prior to get. Otherwise there will be two methods, with one prefixed with has to indicate it is getting whether the value exists or not.

Example

class BalanceApp extends Contract {
    counters = BoxMap<Address, uint64>();

    getBalance(addr: Address): void {
        // Set balance to 0 if addr balance doesn't exist
        const balance = addr.hasBalance ? addr.balance : 0

        // set counter to 1 if it doesn't already exist
        const newCounter = this.counters(addr).exists ? this.counters(addr).value + 1 : 1
        this.counters(addr).value = newCounter
    }
}