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Merge pull request #1751 from rikublock/riku/b0079-ms3

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[Bounty 0079] Python code samples for Decentralized Exchange
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Rome Reginelli
2023-04-20 12:07:00 -07:00
committed by GitHub
parent 49684b4391 01febf201c
commit 90aa6d0ce4
4 changed files with 285 additions and 5 deletions
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content/_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js
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@@ -37,7 +37,7 @@ async function main() {
// 25 TST * 10 XRP per TST * 15% financial exchange (FX) cost
value: xrpl.xrpToDrops(25*10*1.15)
}
// "Quality" is defined as TakerPays ÷ TakerGets. The lower the "quality"
// "Quality" is defined as TakerPays / TakerGets. The lower the "quality"
// number, the better the proposed exchange rate is for the taker.
// The quality is rounded to a number of significant digits based on the
// issuer's TickSize value (or the lesser of the two for token-token trades.)

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content/_code-samples/trade-in-the-decentralized-exchange/py/README.md Normal file
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@@ -0,0 +1,3 @@
# Trade in the Decentralized Exchange
This code demonstrates how to buy a fungible token on the XRP Ledger's decentralized exchange (DEX). For a detailed explanation of how to trade using the DEX, see <https://xrpl.org/trade-in-the-decentralized-exchange.html>.

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content/_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py Normal file
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@@ -0,0 +1,251 @@
import asyncio
import pprint
from decimal import Decimal
from xrpl.asyncio.clients import AsyncWebsocketClient
from xrpl.asyncio.transaction import (
safe_sign_and_autofill_transaction,
send_reliable_submission,
)
from xrpl.asyncio.wallet import generate_faucet_wallet
from xrpl.models.currencies import (
IssuedCurrency,
XRP,
)
from xrpl.models.requests import (
AccountLines,
AccountOffers,
BookOffers,
)
from xrpl.models.transactions import OfferCreate
from xrpl.utils import (
drops_to_xrp,
get_balance_changes,
xrp_to_drops,
)
async def main() -> int:
# Define the network client
async with AsyncWebsocketClient("wss://s.altnet.rippletest.net:51233") as client:
# Get credentials from the Testnet Faucet -----------------------------------
print("Requesting addresses from the Testnet faucet...")
wallet = await generate_faucet_wallet(client, debug=True)
# Define the proposed trade. ------------------------------------------------
# Technically you don't need to specify the amounts (in the "value" field)
# to look up order books using book_offers, but for this tutorial we reuse
# these variables to construct the actual Offer later.
#
# Note that XRP is represented as drops, whereas any other currency is
# represented as a decimal value.
we_want = {
"currency": IssuedCurrency(
currency="TST",
issuer="rP9jPyP5kyvFRb6ZiRghAGw5u8SGAmU4bd"
),
"value": "25",
}
we_spend = {
"currency": XRP(),
# 25 TST * 10 XRP per TST * 15% financial exchange (FX) cost
"value": xrp_to_drops(25 * 10 * 1.15),
}
# "Quality" is defined as TakerPays / TakerGets. The lower the "quality"
# number, the better the proposed exchange rate is for the taker.
# The quality is rounded to a number of significant digits based on the
# issuer's TickSize value (or the lesser of the two for token-token trades).
proposed_quality = Decimal(we_spend["value"]) / Decimal(we_want["value"])
# Look up Offers. -----------------------------------------------------------
# To buy TST, look up Offers where "TakerGets" is TST:
print("Requesting orderbook information...")
orderbook_info = await client.request(
BookOffers(
taker=wallet.classic_address,
ledger_index="current",
taker_gets=we_want["currency"],
taker_pays=we_spend["currency"],
limit=10,
)
)
print(f"Orderbook:\n{pprint.pformat(orderbook_info.result)}")
# Estimate whether a proposed Offer would execute immediately, and...
# If so, how much of it? (Partial execution is possible)
# If not, how much liquidity is above it? (How deep in the order book would
# other Offers have to go before ours would get taken?)
# Note: These estimates can be thrown off by rounding if the token issuer
# uses a TickSize setting other than the default (15). In that case, you
# can increase the TakerGets amount of your final Offer to compensate.
offers = orderbook_info.result.get("offers", [])
want_amt = Decimal(we_want["value"])
running_total = Decimal(0)
if len(offers) == 0:
print("No Offers in the matching book. Offer probably won't execute immediately.")
else:
for o in offers:
if Decimal(o["quality"]) <= proposed_quality:
print(f"Matching Offer found, funded with {o.get('owner_funds')} "
f"{we_want['currency']}")
running_total += Decimal(o.get("owner_funds", Decimal(0)))
if running_total >= want_amt:
print("Full Offer will probably fill")
break
else:
# Offers are in ascending quality order, so no others after this
# will match either
print("Remaining orders too expensive.")
break
print(f"Total matched: {min(running_total, want_amt)} {we_want['currency']}")
if 0 < running_total < want_amt:
print(f"Remaining {want_amt - running_total} {we_want['currency']} "
"would probably be placed on top of the order book.")
if running_total == 0:
# If part of the Offer was expected to cross, then the rest would be placed
# at the top of the order book. If none did, then there might be other
# Offers going the same direction as ours already on the books with an
# equal or better rate. This code counts how much liquidity is likely to be
# above ours.
#
# Unlike above, this time we check for Offers going the same direction as
# ours, so TakerGets and TakerPays are reversed from the previous
# book_offers request.
print("Requesting second orderbook information...")
orderbook2_info = await client.request(
BookOffers(
taker=wallet.classic_address,
ledger_index="current",
taker_gets=we_spend["currency"],
taker_pays=we_want["currency"],
limit=10,
)
)
print(f"Orderbook2:\n{pprint.pformat(orderbook2_info.result)}")
# Since TakerGets/TakerPays are reversed, the quality is the inverse.
# You could also calculate this as 1 / proposed_quality.
offered_quality = Decimal(we_want["value"]) / Decimal(we_spend["value"])
tally_currency = we_spend["currency"]
if isinstance(tally_currency, XRP):
tally_currency = f"drops of {tally_currency}"
offers2 = orderbook2_info.result.get("offers", [])
running_total2 = Decimal(0)
if len(offers2) == 0:
print("No similar Offers in the book. Ours would be the first.")
else:
for o in offers2:
if Decimal(o["quality"]) <= offered_quality:
print(f"Existing offer found, funded with {o.get('owner_funds')} "
f"{tally_currency}")
running_total2 += Decimal(o.get("owner_funds", Decimal(0)))
else:
print("Remaining orders are below where ours would be placed.")
break
print(f"Our Offer would be placed below at least {running_total2} "
f"{tally_currency}")
if 0 < running_total2 < want_amt:
print(f"Remaining {want_amt - running_total2} {tally_currency} "
"will probably be placed on top of the order book.")
# Send OfferCreate transaction ----------------------------------------------
# For this tutorial, we already know that TST is pegged to
# XRP at a rate of approximately 10:1 plus spread, so we use
# hard-coded TakerGets and TakerPays amounts.
tx = OfferCreate(
account=wallet.classic_address,
taker_gets=we_spend["value"],
taker_pays=we_want["currency"].to_amount(we_want["value"]),
)
# Sign and autofill the transaction (ready to submit)
signed_tx = await safe_sign_and_autofill_transaction(tx, wallet, client)
print("Transaction:", signed_tx)
# Submit the transaction and wait for response (validated or rejected)
print("Sending OfferCreate transaction...")
result = await send_reliable_submission(signed_tx, client)
if result.is_successful():
print(f"Transaction succeeded: "
f"https://testnet.xrpl.org/transactions/{signed_tx.get_hash()}")
else:
raise Exception(f"Error sending transaction: {result}")
# Check metadata ------------------------------------------------------------
balance_changes = get_balance_changes(result.result["meta"])
print(f"Balance Changes:\n{pprint.pformat(balance_changes)}")
# For educational purposes the transaction metadata is analyzed manually in the
# following section. However, there is also a get_order_book_changes(metadata)
# utility function available in the xrpl library, which is generally the easier
# and preferred choice for parsing the metadata and computing orderbook changes.
# Helper to convert an XRPL amount to a string for display
def amt_str(amt) -> str:
if isinstance(amt, str):
return f"{drops_to_xrp(amt)} XRP"
else:
return f"{amt['value']} {amt['currency']}.{amt['issuer']}"
offers_affected = 0
for affnode in result.result["meta"]["AffectedNodes"]:
if "ModifiedNode" in affnode:
if affnode["ModifiedNode"]["LedgerEntryType"] == "Offer":
# Usually a ModifiedNode of type Offer indicates a previous Offer that
# was partially consumed by this one.
offers_affected += 1
elif "DeletedNode" in affnode:
if affnode["DeletedNode"]["LedgerEntryType"] == "Offer":
# The removed Offer may have been fully consumed, or it may have been
# found to be expired or unfunded.
offers_affected += 1
elif "CreatedNode" in affnode:
if affnode["CreatedNode"]["LedgerEntryType"] == "RippleState":
print("Created a trust line.")
elif affnode["CreatedNode"]["LedgerEntryType"] == "Offer":
offer = affnode["CreatedNode"]["NewFields"]
print(f"Created an Offer owned by {offer['Account']} with "
f"TakerGets={amt_str(offer['TakerGets'])} and "
f"TakerPays={amt_str(offer['TakerPays'])}.")
print(f"Modified or removed {offers_affected} matching Offer(s)")
# Check balances ------------------------------------------------------------
print("Getting address balances as of validated ledger...")
balances = await client.request(
AccountLines(
account=wallet.classic_address,
ledger_index="validated",
)
)
pprint.pp(balances.result)
# Check Offers --------------------------------------------------------------
print(f"Getting outstanding Offers from {wallet.classic_address} "
f"as of validated ledger...")
acct_offers = await client.request(
AccountOffers(
account=wallet.classic_address,
ledger_index="validated",
)
)
pprint.pp(acct_offers.result)
# End main()
return 0
if __name__ == "__main__":
asyncio.run(main())

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content/tutorials/use-tokens/trade-in-the-decentralized-exchange.md
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@@ -14,14 +14,16 @@ This tutorial demonstrates how you can buy and sell tokens in the [decentralized
## Prerequisites
- You need a connection to the XRP Ledger network. As shown in this tutorial, you can use public servers for testing.
- You should be familiar with the Getting Started instructions for your preferred client library. This page provides examples for the following:
- **JavaScript** with the [xrpl.js library](https://github.com/XRPLF/xrpl.js/). See [Get Started Using JavaScript](get-started-using-javascript.html) for setup steps.
- **Python** with the [`xrpl-py` library](https://xrpl-py.readthedocs.io/). See [Get Started using Python](get-started-using-python.html) for setup steps.
- You can also read along and use the interactive steps in your browser without any setup.
<!-- Source for this specific tutorial's interactive bits: -->
<script src='https://cdn.jsdelivr.net/npm/bignumber.js@9.0.2/bignumber.min.js'></script>
<script type="application/javascript" src="assets/js/tutorials/trade-in-the-dex.js"></script>
This page provides JavaScript examples that use the [xrpl.js](https://js.xrpl.org/) library. See [Get Started Using JavaScript](get-started-using-javascript.html) for setup instructions.
Since JavaScript works in the web browser, you can read along and use the interactive steps without any setup.
## Example Code
Complete sample code for all of the steps of this tutorial is available under the [MIT license](https://github.com/XRPLF/xrpl-dev-portal/blob/master/LICENSE).
@@ -49,6 +51,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/base-with-bignumber.js", language="js") }}
_Python_
{{ include_code("_code-samples/get-started/py/base-async.py", language="py") }}
<!-- MULTICODE_BLOCK_END -->
**Note:** The JavaScript code samples in this tutorial use the [`async`/`await` pattern](https://javascript.info/async-await). Since `await` needs to be used from within an `async` function, the remaining code samples are written to continue inside the `main()` function started here. You can also use Promise methods `.then()` and `.catch()` instead of `async`/`await` if you prefer.
@@ -71,6 +77,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js", language="js", start_with="// Get credentials", end_before="// Define the proposed trade") }}
_Python_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py", language="py", start_with="# Get credentials", end_before="# Define the proposed trade") }}
<!-- MULTICODE_BLOCK_END -->
### {{n.next()}}. Look Up Offers
@@ -87,6 +97,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js", language="js", start_with="// Define the proposed trade", end_before="// Send OfferCreate") }}
_Python_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py", language="py", start_with="# Define the proposed trade", end_before="# Send OfferCreate") }}
<!-- MULTICODE_BLOCK_END -->
**Note:** Other users of the XRP Ledger can also make trades at any time, so this is only an estimate of what would happen if nothing else changes. The outcome of a transaction is not guaranteed until it is [final](finality-of-results.html).
@@ -153,6 +167,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js", language="js", start_with="// Send OfferCreate", end_before="// Check metadata") }}
_Python_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py", language="py", start_with="# Send OfferCreate", end_before="# Check metadata") }}
<!-- MULTICODE_BLOCK_END -->
You can use this interface to send the transaction specified by the amounts in the previous step:
@@ -187,6 +205,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js", language="js", start_with="// Check metadata", end_before="// Check balances") }}
_Python_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py", language="py", start_with="# Check metadata", end_before="# Check balances") }}
<!-- MULTICODE_BLOCK_END -->
You can use this interface to test it out:
@@ -210,6 +232,10 @@ _JavaScript_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/js/trade-in-the-dex.js", language="js", start_with="// Check balances", end_before="client.disconnect()") }}
_Python_
{{ include_code("_code-samples/trade-in-the-decentralized-exchange/py/trade-in-the-dex.py", language="py", start_with="# Check balances", end_before="# End main()") }}
<!-- MULTICODE_BLOCK_END -->
You can use this interface to test it out: