Transaction Fields and Global Parameters¶

PyTeal smart contracts can access properties of the current transaction and the state of the blockchain when they are running.

Transaction Fields¶

Information about the current transaction being evaluated can be obtained using the Txn object using the PyTeal expressions shown below.

Since numerous transaction fields exist, the fields are logically organized into tables by transaction type.

Fields by Transaction Type¶

Common Fields¶

Operator	Type	Min TEAL Version	Notes
`Txn.type()`	`TealType.bytes`	2
`Txn.type_enum()`	`TealType.uint64`	2	see table below
`Txn.sender()`	`TealType.bytes`	2	32 byte address
`Txn.fee()`	`TealType.uint64`	2	in microAlgos
`Txn.first_valid()`	`TealType.uint64`	2	round number
`Txn.last_valid()`	`TealType.uint64`	2	round number
`Txn.note()`	`TealType.bytes`	2	transaction note in bytes
`Txn.lease()`	`TealType.bytes`	2	transaction lease in bytes
`Txn.group_index()`	`TealType.uint64`	2	position of this transaction within a transaction group, starting at 0
`Txn.tx_id()`	`TealType.bytes`	2	the computed ID for this transaction, 32 bytes
`Txn.rekey_to()`	`TealType.bytes`	2	32 byte address

Application Call¶

Operator	Type	Min TEAL Version	Notes
`Txn.application_id()`	`TealType.uint64`	2
`Txn.on_completion()`	`TealType.uint64`	2
`Txn.approval_program()`	`TealType.bytes`	2
`Txn.global_num_uints()`	`TealType.uint64`	3	Maximum global integers in app schema
`Txn.global_num_byte_slices()`	`TealType.uint64`	3	Maximum global byte strings in app schema
`Txn.local_num_uints()`	`TealType.uint64`	3	Maximum local integers in app schema
`Txn.local_num_byte_slices()`	`TealType.uint64`	3	Maximum local byte strings in app schema
`Txn.accounts`	`TealType.bytes[]`	2	Array of application accounts
`Txn.assets`	`TealType.uint64[]`	3	Array of application assets
`Txn.applications`	`TealType.uint64[]`	3	Array of applications
`Txn.clear_state_program()`	`TealType.bytes`	2
`Txn.extra_program_pages()`	`TealType.uint64`	4	Number of extra program pages for app
`Txn.application_args`	`TealType.bytes[]`	2	Array of application arguments
`Txn.created_application_id()`	`TealType.uint64`	5	The ID of the newly created application in this transaction. In v5, only valid on inner transactions. >= v6 works with top-level and inner transactions.
`Txn.logs`	`TealType.bytes[]`	5	Array of application logged items. In v5, only valid on inner transactions. >= v6 works with top-level and inner transactions.
`Txn.last_log()`	`TealType.bytes[]`	6	The last message emitted. Empty bytes if none were emitted. Application mode only.

Asset Config¶

Operator	Type	Min TEAL Version	Notes
`Txn.config_asset()`	`TealType.uint64`	2	ID of asset being configured
`Txn.config_asset_total()`	`TealType.uint64`	2
`Txn.config_asset_decimals()`	`TealType.uint64`	2
`Txn.config_asset_default_frozen()`	`TealType.uint64`	2
`Txn.config_asset_unit_name()`	`TealType.bytes`	2
`Txn.config_asset_name()`	`TealType.bytes`	2
`Txn.config_asset_url()`	`TealType.bytes`	2
`Txn.config_asset_metadata_hash()`	`TealType.bytes`	2
`Txn.config_asset_manager()`	`TealType.bytes`	2	32 byte address
`Txn.config_asset_reserve()`	`TealType.bytes`	2	32 byte address
`Txn.config_asset_freeze()`	`TealType.bytes`	2	32 byte address
`Txn.config_asset_clawback()`	`TealType.bytes`	2	32 byte address
`Txn.created_asset_id()`	`TealType.uint64`	5	The ID of the newly created asset in this transaction. In v5, only valid on inner transactions. >= v6 works with top-level and inner transactions.

Asset Freeze¶

Operator	Type	Min TEAL Version	Notes
`Txn.freeze_asset()`	`TealType.uint64`	2
`Txn.freeze_asset_account()`	`TealType.bytes`	2	32 byte address
`Txn.freeze_asset_frozen()`	`TealType.uint64`	2

Asset Transfer¶

Operator	Type	Min TEAL Version	Notes
`Txn.xfer_asset()`	`TealType.uint64`	2	ID of asset being transferred
`Txn.asset_amount()`	`TealType.uint64`	2	value in Asset’s units
`Txn.asset_sender()`	`TealType.bytes`	2	32 byte address, causes clawback of all value if sender is the clawback
`Txn.asset_receiver()`	`TealType.bytes`	2	32 byte address
`Txn.asset_close_to()`	`TealType.bytes`	2	32 byte address

Key Registration¶

Operator	Type	Min TEAL Version	Notes
`Txn.vote_pk()`	`TealType.bytes`	2	32 byte address
`Txn.selection_pk()`	`TealType.bytes`	2	32 byte address
`Txn.state_proof_pk`	`TealType.bytes`	6	64 byte state proof public key commitment.
`Txn.vote_first()`	`TealType.uint64`	2
`Txn.vote_last()`	`TealType.uint64`	2
`Txn.vote_key_dilution()`	`TealType.uint64`	2
`Txn.nonparticipation()`	`TealType.uint64`	5	Marks an account nonparticipating for rewards

Payment¶

Operator	Type	Min TEAL Version	Notes
`Txn.receiver()`	`TealType.bytes`	2	32 byte address
`Txn.amount()`	`TealType.uint64`	2	in microAlgos
`Txn.close_remainder_to()`	`TealType.bytes`	2	32 byte address

Transaction Types¶

The Txn.type_enum() values can be checked using the TxnType enum:

Value	Numerical Value	Type String	Description
`TxnType.Unknown`	`0`	unknown	unknown type, invalid
`TxnType.Payment`	`1`	pay	payment
`TxnType.KeyRegistration`	`2`	keyreg	key registration
`TxnType.AssetConfig`	`3`	acfg	asset config
`TxnType.AssetTransfer`	`4`	axfer	asset transfer
`TxnType.AssetFreeze`	`5`	afrz	asset freeze
`TxnType.ApplicationCall`	`6`	appl	application call

Transaction Array Fields¶

Some of the exposed transaction fields are arrays with the type TealType.uint64[] or TealType.bytes[]. These fields are Txn.application_args, Txn.assets, Txn.accounts, Txn.applications, and InnerTxn.logs.

The length of these array fields can be found using the .length() method, and individual items can be accessed using bracket notation. For example:

Txn.application_args.length() # get the number of application arguments in the transaction
Txn.application_args[0] # get the first application argument
Txn.application_args[1] # get the second application argument

# as of TEAL v5, PyTeal expressions can be used to dynamically index into array properties as well
Txn.application_args[Txn.application_args.length() - Int(1)] # get the last application argument

Special case: `Txn.accounts` and `Txn.applications`¶

The Txn.accounts and Txn.applications arrays are special cases. Normal arrays in PyTeal are 0-indexed, but these are 1-indexed with special values at index 0.

For the accounts array, Txn.accounts[0] is always equivalent to Txn.sender().

For the applications array, Txn.applications[0] is always equivalent to Txn.application_id().

IMPORTANT: Since these arrays are 1-indexed, their lengths are handled differently. For example, if Txn.accounts.length() or Txn.applications.length() is 2, then indexes 0, 1, and 2 will be present. In fact, the index 0 will always evaluate to the special values above, even when length() is 0.

Atomic Transfer Groups¶

Atomic Transfers are irreducible batch transactions that allow groups of transactions to be submitted at one time. If any of the transactions fail, then all the transactions will fail. PyTeal allows programs to access information about the transactions in an atomic transfer group using the Gtxn object. This object acts like a list of TxnObject, meaning all of the above transaction fields on Txn are available on the elements of Gtxn. For example:

Gtxn[0].sender() # get the sender of the first transaction in the atomic transfer group
Gtxn[1].receiver() # get the receiver of the second transaction in the atomic transfer group

# as of TEAL v3, PyTeal expressions can be used to dynamically index into Gtxn as well
Gtxn[Txn.group_index() - Int(1)].sender() # get the sender of the previous transaction in the atomic transfer group

Gtxn is zero-indexed and the maximum size of an atomic transfer group is 16. The size of the current transaction group is available as Global.group_size(). A standalone transaction will have a group size of 1.

To find the current transaction’s index in the transfer group, use Txn.group_index(). If the current transaction is standalone, it’s group index will be 0.

Inner Transactions¶

Note

Inner transactions are only available in TEAL version 5 or higher.

Inner transactions can be created and submitted with expressions from the InnerTxnBuilder class. The properties of the most recently submitted inner transaction can be accessed using the InnerTxn object. This object is an instance of TxnObject, meaning all of the above transaction fields on Txn are available on InnerTxn as well.

Global Parameters¶

Information about the current state of the blockchain can be obtained using the following Global expressions:

Operator	Type	Min TEAL Version	Notes
`Global.min_txn_fee()`	`TealType.uint64`	2	in microAlgos
`Global.min_balance()`	`TealType.uint64`	2	in mircoAlgos
`Global.max_txn_life()`	`TealType.uint64`	2	number of rounds
`Global.zero_address()`	`TealType.bytes`	2	32 byte address of all zero bytes
`Global.group_size()`	`TealType.uint64`	2	number of txns in this atomic transaction group, at least 1
`Global.logic_sig_version()`	`TealType.uint64`	2	the maximum supported TEAL version
`Global.round()`	`TealType.uint64`	2	the current round number
`Global.latest_timestamp()`	`TealType.uint64`	2	the latest confirmed block UNIX timestamp
`Global.current_application_id()`	`TealType.uint64`	2	the ID of the current application executing
`Global.creator_address()`	`TealType.bytes`	3	32 byte address of the creator of the current application
`Global.current_application_address()`	`TealType.bytes`	5	32 byte address of the current application controlled account
`Global.group_id()`	`TealType.bytes`	5	32 byte ID of the current transaction group

Transaction Fields and Global Parameters¶