Transactions¶
Algorand Python provides types for accessing fields of other transactions in a group, as well as creating and submitting inner transactions from your smart contract.
The following types are available:
Group Transactions |
Inner Transaction Field sets |
Inner Transaction |
|---|---|---|
Group Transactions¶
Group transactions can be used as ARC4 parameters or instantiated from a group index.
ARC4 parameter¶
Group transactions can be used as parameters in ARC4 method
For example to require a payment transaction in an ARC4 ABI method:
import algopy
class MyContract(algopy.ARC4Contract):
@algopy.arc4.abimethod()
def process_payment(self: algopy.gtxn.PaymentTransaction) -> None:
...
Group Index¶
Group transactions can also be created using the group index of the transaction. If instantiating one of the type specific transactions they will be checked to ensure the transaction is of the expected type. Transaction is not checked for a specific type and provides access to all transaction fields
For example, to obtain a reference to a payment transaction:
import algopy
@algopy.subroutine()
def process_payment(group_index: algopy.UInt64) -> None:
pay_txn = algopy.gtxn.PaymentTransaction(group_index)
...
Inner Transactions¶
Inner transactions are defined using the parameter types, and can then be submitted individually by calling the
.submit() method, or as a group by calling submit_txns
Examples¶
Create and submit an inner transaction¶
from algopy import Account, UInt64, itxn, subroutine
@subroutine
def example(amount: UInt64, receiver: Account) -> None:
itxn.Payment(
amount=amount,
receiver=receiver,
fee=0,
).submit()
Accessing result of a submitted inner transaction¶
from algopy import Asset, itxn, subroutine
@subroutine
def example() -> Asset:
asset_txn = itxn.AssetConfig(
asset_name=b"Puya",
unit_name=b"PYA",
total=1000,
decimals=3,
fee=0,
).submit()
return asset_txn.created_asset
Submitting multiple transactions¶
from algopy import Asset, Bytes, itxn, log, subroutine
@subroutine
def example() -> tuple[Asset, Bytes]:
asset1_params = itxn.AssetConfig(
asset_name=b"Puya",
unit_name=b"PYA",
total=1000,
decimals=3,
fee=0,
)
app_params = itxn.ApplicationCall(
app_id=1234,
app_args=(Bytes(b"arg1"), Bytes(b"arg1"))
)
asset1_txn, app_txn = itxn.submit_txns(asset1_params, app_params)
# log some details
log(app_txn.logs(0))
log(asset1_txn.txn_id)
log(app_txn.txn_id)
return asset1_txn.created_asset, app_txn.logs(1)
Create an ARC4 application, and then call it¶
from algopy import Bytes, arc4, itxn, subroutine
HELLO_WORLD_APPROVAL: bytes = ...
HELLO_WORLD_CLEAR: bytes = ...
@subroutine
def example() -> None:
# create an application
application_txn = itxn.ApplicationCall(
approval_program=HELLO_WORLD_APPROVAL,
clear_state_program=HELLO_WORLD_CLEAR,
fee=0,
).submit()
app = application_txn.created_app
# invoke an ABI method
call_txn = itxn.ApplicationCall(
app_id=app,
app_args=(arc4.arc4_signature("hello(string)string"), arc4.String("World")),
fee=0,
).submit()
# extract result
hello_world_result = arc4.String.from_log(call_txn.last_log)
# OR, call it automatic ARC4 encoding, type validation and result handling
hello_world_result, call_txn = arc4.abi_call[arc4.String]( # declare return type
"hello(string)string", # method signature to call
"again", # abi method arguments
fee=0, # other transaction parameters
app_id=app
)
Create and submit transactions in a loop¶
from algopy import Account, UInt64, itxn, subroutine
@subroutine
def example(receivers: tuple[Account, Account, Account]) -> None:
for receiver in receivers:
itxn.Payment(
amount=UInt64(1_000_000),
receiver=receiver,
fee=0,
).submit()
Limitations¶
Inner transactions are powerful, but currently do have some restrictions in how they are used.
Inner transaction objects cannot be passed to or returned from subroutines¶
from algopy import Application, Bytes, itxn, subroutine
@subroutine
def parameter_not_allowed(txn: itxn.PaymentInnerTransaction) -> None:
# this is a compile error
...
@subroutine
def return_not_allowed() -> itxn.PaymentInnerTransaction:
# this is a compile error
...
@subroutine
def passing_fields_allowed() -> Application:
txn = itxn.ApplicationCall(...).submit()
do_something(txn.txn_id, txn.logs(0)) # this is ok
return txn.created_app # and this is ok
@subroutine
def do_something(txn_id: Bytes): # this is just a regular subroutine
...
Inner transaction parameters cannot be reassigned without a .copy()¶
from algopy import itxn, subroutine
@subroutine
def example() -> None:
payment = itxn.Payment(...)
reassigned_payment = payment # this is an error
copied_payment = payment.copy() # this is ok
Inner transactions cannot be reassigned¶
from algopy import itxn, subroutine
@subroutine
def example() -> None:
payment_txn = itxn.Payment(...).submit()
reassigned_payment_txn = payment_txn # this is an error
txn_id = payment_txn.txn_id # this is ok
Inner transactions methods cannot be called if there is a subsequent inner transaction submitted or another subroutine is called.¶
from algopy import itxn, subroutine
@subroutine
def example() -> None:
app_1 = itxn.ApplicationCall(...).submit()
log_from_call1 = app_1.logs(0) # this is ok
# another inner transaction is submitted
itxn.ApplicationCall(...).submit()
# or another subroutine is called
call_some_other_subroutine()
app1_txn_id = app_1.txn_id # this is ok, properties are still available
another_log_from_call1 = app_1.logs(1) # this is not allowed as the array results may no longer be available, instead assign to a variable before submitting another transaction