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Transaction Parameters

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Description

Section titled “Description”

This example demonstrates how to get suggested transaction parameters using suggested_params(). These parameters are essential for constructing valid transactions on the Algorand network. Prerequisites:

Prerequisites

Section titled “Prerequisites”
  • LocalNet running (via algokit localnet start)

Run This Example

Section titled “Run This Example”

From the repository’s examples directory:

Terminal window
cd examples
uv run python algod_client/05_transaction_params.py

Code

Section titled “Code”

View source on GitHub

05_transaction_params.py
# ruff: noqa: N999, C901, PLR0912, PLR0915
"""
Example: Transaction Parameters


This example demonstrates how to get suggested transaction parameters using
suggested_params(). These parameters are essential for constructing valid
transactions on the Algorand network.


Prerequisites:
- LocalNet running (via `algokit localnet start`)
"""


import base64


from shared import (
    create_algod_client,
    print_error,
    print_header,
    print_info,
    print_step,
    print_success,
)




def format_as_base64(data: bytes | str) -> str:
    """Format bytes or base64 string for display."""
    if isinstance(data, bytes):
        return base64.b64encode(data).decode("utf-8")
    return data




def format_fee(micro_algos: int) -> str:
    """Format a fee as microAlgos and Algos."""
    algo_value = micro_algos / 1_000_000
    return f"{micro_algos:,} uALGO ({algo_value:.6f} ALGO)"




def main() -> None:
    print_header("Transaction Parameters Example")


    # Create an Algod client connected to LocalNet
    algod = create_algod_client()


    # =========================================================================
    # Step 1: Get Suggested Parameters using suggested_params()
    # =========================================================================
    print_step(1, "Getting suggested transaction parameters with suggested_params()")


    try:
        suggested_params = algod.suggested_params()


        print_success("Suggested parameters retrieved successfully!")
        print_info("")


        # =====================================================================
        # Step 2: Display Core Parameters
        # =====================================================================
        print_step(2, "Displaying suggested transaction parameters")


        print_info("Core Transaction Parameters:")
        print_info(f"  fee:              {format_fee(suggested_params.fee)}")
        print_info(f"  min_fee:          {format_fee(suggested_params.min_fee)}")
        print_info(f"  flat_fee:         {suggested_params.flat_fee}")
        print_info("")


        # =====================================================================
        # Step 3: Display Validity Window Parameters
        # =====================================================================
        print_step(3, "Displaying validity window parameters (first_valid, last_valid)")


        print_info("Validity Window:")
        print_info(f"  first_valid:      {suggested_params.first_valid:,}")
        print_info(f"  last_valid:       {suggested_params.last_valid:,}")
        print_info("")


        validity_window = suggested_params.last_valid - suggested_params.first_valid
        print_info(f"  Validity Window:  {validity_window:,} rounds")
        print_info("The default validity window is 1000 rounds (~1 hour on MainNet)")
        print_info("A transaction is only valid between first_valid and last_valid rounds")
        print_info("")


        # =====================================================================
        # Step 4: Display Network Identification Parameters
        # =====================================================================
        print_step(4, "Displaying network identification parameters")


        print_info("Network Identification:")
        print_info(f"  genesis_id:        {suggested_params.genesis_id}")
        print_info(f"  genesis_hash:      {format_as_base64(suggested_params.genesis_hash)}")
        print_info(f"  consensus_version: {suggested_params.consensus_version}")
        print_info("")


        print_info("genesis_id and genesis_hash uniquely identify the network")
        print_info("Transactions are rejected if sent to the wrong network")
        print_info("")


        # =====================================================================
        # Step 5: Explain Each Parameter's Purpose
        # =====================================================================
        print_step(5, "Explaining each parameter's purpose")


        print_info("Parameter Purposes:")
        print_info("")
        print_info("  fee:")
        print_info("    The suggested fee per byte for the transaction.")
        print_info("    During network congestion, this value may increase.")
        print_info("")
        print_info("  min_fee:")
        print_info("    The minimum fee required regardless of transaction size.")
        print_info("    Currently 1000 uALGO (0.001 ALGO) on all Algorand networks.")
        print_info("")
        print_info("  flat_fee:")
        print_info("    When false, fee is calculated as: fee * transactionSize")
        print_info("    When true, fee is used directly as the total fee.")
        print_info("")
        print_info("  first_valid:")
        print_info("    The first round this transaction is valid for.")
        print_info("    Usually set to the current round from the node.")
        print_info("")
        print_info("  last_valid:")
        print_info("    The last round this transaction is valid for.")
        print_info("    Transaction will fail if not confirmed by this round.")
        print_info("")
        print_info("  genesis_id:")
        print_info('    A human-readable network identifier (e.g., "mainnet-v1.0").')
        print_info("    Prevents replaying transactions across networks.")
        print_info("")
        print_info("  genesis_hash:")
        print_info("    The SHA256 hash of the genesis block, uniquely identifying the network.")
        print_info("    Cryptographically ensures transaction is for the correct chain.")
        print_info("")
        print_info("  consensus_version:")
        print_info("    The consensus protocol version at the current round.")
        print_info("    Indicates which features and rules are active.")
        print_info("")


        # =====================================================================
        # Step 6: Demonstrate Customizing Parameters
        # =====================================================================
        print_step(6, "Demonstrating how to customize transaction parameters")


        print_info("Customizing Parameters:")
        print_info("")


        # Example 1: Setting a specific flat fee
        custom_fee_value = 2000  # Set a fixed 2000 uALGO fee


        print_info("  Example 1: Setting a flat fee")
        print_info(f"    Original fee:      {format_fee(suggested_params.fee)}")
        print_info(f"    Original flat_fee: {suggested_params.flat_fee}")
        print_info(f"    Custom fee:        {format_fee(custom_fee_value)}")
        print_info("    Custom flat_fee:   True")
        print_info("Set flat_fee=True to use a fixed fee instead of per-byte")
        print_info("")


        # Example 2: Extending the validity window
        first_valid = suggested_params.first_valid
        last_valid = suggested_params.last_valid
        extended_window = 2000  # 2000 rounds instead of default 1000
        extended_last_valid = first_valid + extended_window


        print_info("  Example 2: Extending the validity window")
        print_info(f"    Original last_valid:  {last_valid:,}")
        print_info(f"    Extended last_valid:  {extended_last_valid:,}")
        print_info(f"    Original window:      {validity_window:,} rounds")
        print_info(f"    Extended window:      {extended_window:,} rounds")
        print_info("Extend validity window for offline signing or delayed submission")
        print_info("")


        # Example 3: Shortening the validity window
        short_window = 100  # Only 100 rounds validity
        short_last_valid = first_valid + short_window


        print_info("  Example 3: Shortening the validity window")
        print_info(f"    Original last_valid:  {last_valid:,}")
        print_info(f"    Shortened last_valid: {short_last_valid:,}")
        print_info(f"    Shortened window:     {short_window:,} rounds")
        print_info("Shorter windows provide better replay protection")
        print_info("")


        # Example 4: Setting a specific first_valid for delayed execution
        future_round = first_valid + 10  # Valid starting 10 rounds from now
        future_last_valid = future_round + 1000


        print_info("  Example 4: Delayed execution (future first_valid)")
        print_info(f"    Original first_valid: {first_valid:,}")
        print_info(f"    Delayed first_valid:  {future_round:,}")
        print_info(f"    Delayed last_valid:   {future_last_valid:,}")
        print_info("Set future first_valid to prevent immediate execution")


    except Exception as e:
        print_error(f"Failed to get transaction parameters: {e}")
        print_info("Make sure LocalNet is running with `algokit localnet start`")
        raise SystemExit(1) from e


    # =========================================================================
    # Summary
    # =========================================================================
    print_header("Summary")
    print_info("This example demonstrated:")
    print_info("  1. suggested_params() - Get parameters for building transactions")
    print_info("  2. Parameter fields: fee, min_fee, flat_fee, first_valid, last_valid")
    print_info("  3. Network identification: genesis_id, genesis_hash, consensus_version")
    print_info("  4. How first_valid and last_valid define the validity window")
    print_info("  5. Customizing parameters: fees and validity windows")
    print_info("")
    print_info("Key suggested_params fields:")
    print_info("  - fee: Suggested fee per byte (int)")
    print_info("  - min_fee: Minimum transaction fee (int)")
    print_info("  - flat_fee: Whether fee is flat or per-byte (bool)")
    print_info("  - first_valid: First valid round (int)")
    print_info("  - last_valid: Last valid round (int)")
    print_info("  - genesis_id: Network identifier string")
    print_info("  - genesis_hash: Genesis block hash (base64 string)")
    print_info("  - consensus_version: Protocol version string")
    print_info("")
    print_info("Use cases:")
    print_info("  - Building transactions with correct fees")
    print_info("  - Setting appropriate validity windows")
    print_info("  - Ensuring network compatibility")
    print_info("  - Offline transaction signing with extended windows")




if __name__ == "__main__":
    main()

Other examples in Algod Client

Section titled “Other examples in Algod Client”