Logging

Algorand Python provides a log method that allows you to emit debugging and event information as well as return values from your contracts to the caller.

This log method is a superset of the AVM log method that adds extra functionality:

• You can log multiple items rather than a single item
• Items are concatenated together with an optional separator (which defaults to: "")
• Items are automatically converted to bytes for you
• Support for:
  • int literals / module variables (encoded as raw bytes, not ASCII)
  • UInt64 values (encoded as raw bytes, not ASCII)
  • str literals / module variables (encoded as UTF-8)
  • bytes literals / module variables (encoded as is)
  • Bytes values (encoded as is)
  • BytesBacked values, which includes String, BigUInt, Account and all of the ARC-4 types (encoded as their underlying bytes values)

Logged values are available to the calling client and attached to the transaction record stored on the blockchain ledger.

If you want to emit ARC-28 events in the logs then there is a purpose-built function for that.

Here’s an example contract that uses the log method in various ways:

from algopy import BigUInt, Bytes, Contract, log, op

class MyContract(Contract):

def approval_program(self) -> bool:

log(0)

log(b"1")

log("2")

log(op.Txn.num_app_args + 3)

log(Bytes(b"4") if op.Txn.num_app_args else Bytes())

log(

b"5",

6,

op.Txn.num_app_args + 7,

BigUInt(8),

Bytes(b"9") if op.Txn.num_app_args else Bytes(),

sep="_",

)

return True

def clear_state_program(self) -> bool:

return True