Submitting Transactions and Fees with the Walley Python SDK

This is the core of the SDK: take any ledger Commands batch — your dApp’s own transaction — quote its fee, sign it locally, and submit it. Transfers, preapprovals, and fee payments are all built on this same machinery.

Execute your dApp’s commands

Commands can come from anywhere: your backend, a Walley /prepare endpoint, or hand-built against the Ledger API. Pass a dict or the raw JSON string your dApp emits:

commands = my_dapp.build_transaction(w.party_id)

result = w.transactions.execute(commands)         # prepare → sign → submit → wait
result.update_id                                  # ledger update id
result.fee                                        # the network fee it incurred

w.transactions.execute(commands, wait=False)      # fire-and-forget

In dApp SDK terms, execute(commands) is prepareExecuteAndWait and execute(commands, wait=False) is prepareExecute — minus the popup, since your process holds the key.

Inspect the fee before committing

execute is prepare + submit. Split them to see the fee — or anything else about the prepared transaction — before signing:

prepared = w.transactions.prepare(commands)
prepared.fee            # Fee(amount=Decimal("0.03")) — or None if free

result = w.transactions.submit(prepared)   # commit
# ...or just drop `prepared` — nothing was signed, nothing is owed

Nothing touches the ledger until submit. Under the hood, submit signs the prepared transaction’s hash with your Ed25519 key and echoes the prepared bytes back — Canton’s external-party signing flow, in one call.

The prepaid traffic model

Walley charges Canton network traffic as a fee in CC (Canton Coin): the ledger’s traffic estimate for your transaction is priced in USD and converted at the current CC price. Every prepare quotes it up front; sends inside the daily free allowance quote fee=None (check with w.traffic.free_sends()). Fees are prepaid. You buy a traffic balance ahead of time, and each charged transaction draws from it automatically — there’s no per-transaction settle step:

w.traffic.balance()        # TrafficBalance(available=Decimal("142.50"), ...)
w.traffic.purchase("100")  # buy 100 CC of traffic; drawn down as you transact

purchase is a real on-ledger top-up: it exercises WalleyRules_BuyTraffic, paying CC to the operator, and (like any transaction) it’s prepared, signed, and submitted for you. Buying traffic is itself fee-exempt. You can also credit someone else’s balance:

w.traffic.purchase("100", beneficiary="party::1220…")   # you pay, they receive

One transaction can be fronted: if your traffic balance can’t cover a fee, the charge still goes through and the balance goes negative by that one transaction. While it’s negative, the next prepare fails with InsufficientTrafficError (HTTP 402) until you top up.

from walley import InsufficientTrafficError

try:
    w.transactions.execute(commands)
except InsufficientTrafficError:
    w.traffic.purchase("100")          # top up, then retry
    w.transactions.execute(commands)

Charged fees appear in history with tx_kind="fee" — filter with w.transactions.list(tx_kind="fees") or exclude with "non_fees". Inspect the traffic ledgers directly with w.traffic.usage() (what each transaction was charged) and w.traffic.purchases() (your top-ups).

Transaction history

History is cursor-paginated and scoped to your party:

page = w.transactions.list(page_size=50)
page.transactions[0].event          # TransferEvent | MergeEvent
page.next_cursor                    # pass back as cursor=... for the next page

for tx in w.transactions.iter():    # or walk all pages
    ...

Overview

Typescript SDK (dApp)

Python SDK

gRPC API

Submitting Transactions and Fees with the Walley Python SDK

Execute your dApp’s commands

Inspect the fee before committing

The prepaid traffic model

Transaction history

​Execute your dApp’s commands

​Inspect the fee before committing

​The prepaid traffic model

​Transaction history

Execute your dApp’s commands

Inspect the fee before committing

The prepaid traffic model

Transaction history