Python SDK - Elastly

The elastly package is the supported way to call Elastly from Python. The request and response types are generated from the same OpenAPI contract our servers validate against, so they cannot drift from the API. On top of that it adds what every integration needs: a price call that never breaks your quote screen, typed errors, webhook verification, and a connector that pages, checkpoints, retries, and reports for you.

pip install elastly

Python 3.9 or later.

Keys and scopes

Create API keys under Settings → API keys. Scopes are separate on purpose: a serving key can never write your catalog, and a connector key can never read prices.

Scope	Used for	SDK surface
ERP	Price serving	`PricesNamespace`
Connector	Ingest and write-backs	`IngestApi`, `WritebacksApi`, `define_connector`

import elastly
from elastly.serving import PricesNamespace
from elastly.transport import ElastlyTransport

config = elastly.Configuration(access_token="elastly_live_...")
prices = PricesNamespace(ElastlyTransport(elastly.ApiClient(config)))

The one thing to get right: the decision id

Every priced line comes back with a pricing_decision_id. Store it in your own system, on the quote line it priced. When that quote later closes and you send it back to Elastly, the id ties what Elastly recommended to what your rep actually charged. That difference is what the model learns from. Skip it and everything still looks like it works: prices serve, quotes ingest, dashboards fill. But the model learns nothing from your quotes, and nothing tells you. So wire it first:

result = prices.get(line, fail_open=fail_open)

if result.source == "elastly":
    erp.update_quote_line(
        quote_line_id,
        elastly_price_cents=result.price_cents,
        elastly_decision_id=result.pricing_decision_id,
    )

Price a line, with a fallback

A price call usually runs inside a rep’s quote screen or a checkout render. If Elastly is slow or down, your system must keep working. The SDK makes that a policy you declare, not code you write:

from elastly.serving import static_fallback, FallbackPrice
from elastly.models.prices_request_lines_inner import PricesRequestLinesInner

fail_open = static_fallback(
    lambda line, cause: FallbackPrice(price_cents=erp.list_price(line.product_sku), currency="USD"),
    deadline_ms=800,
)

result = prices.get(
    PricesRequestLinesInner(product_sku="VLV-200", customer_external_id="cust-1042", quantity=25),
    fail_open=fail_open,
)

if result.source == "elastly":
    render(result.price_cents, result.reason_summary)
elif result.source == "fallback":
    render(result.price_cents)  # result.cause.reason tells you why

Under this policy a timeout, a 5xx, a rate limit, a malformed body, or a network failure never raises. The SDK retries where it can, then calls your fallback and returns a result with source == "fallback" and the cause attached. If your fallback returns None, you get source == "unavailable", an explicit typed no-answer. Requests that mean your call is wrong (invalid_request, feature_not_enabled) always raise a typed error, because a bug in your integration is not an outage to paper over. For batch jobs where a wrong price is worse than no price, use throw_on_failure, which raises on everything:

from elastly.serving import throw_on_failure

results = prices.get_many(lines, fail_open=throw_on_failure())

get_many prices up to 100 lines in one HTTP call. One unknown SKU fails that line alone, never the whole batch.

Typed errors

Every error is a typed exception carrying the stable error code and the request id, so support can find the exact call. Catch the specific class or the base:

from elastly import errors

try:
    prices.get(line, fail_open=throw_on_failure())
except errors.RateLimitError as e:
    print(e.retry_after_ms)
except errors.UnknownProductError as e:
    print(e.request_id)
except errors.ApiError as e:
    print(e.code, e.status)

There is one exception per API error code (UnknownProductError, NoCostBasisError, MonthlyVolumeExceededError, and the rest), all subclassing ApiError, which subclasses ElastlyError. Catch ElastlyError to handle anything, including network and timeout faults.

Verify a webhook

from elastly.webhooks import WebhooksNamespace, SignatureVerificationError

webhooks = WebhooksNamespace()

try:
    event = webhooks.verify(raw_body, signature_header, "whsec_...")
except SignatureVerificationError:
    return  # reject with 400

if event.event == "sync.completed":
    print(event.data)

verify checks the signature in constant time, rejects anything older than five minutes, and returns a typed event. It raises SignatureVerificationError on a bad signature, a replay, or a malformed body. The four event types are sync.completed, recommendation.created, price.written_back, and test.ping.

What the SDK handles for you

Idempotency. Every mutating call carries a key that stays stable across retries, so a retried price call can never double-count against your plan.
Retries. Failed calls back off with full jitter and honor Retry-After and RateLimit-Reset.
A circuit breaker. After repeated failures it stops hammering Elastly and goes straight to your fallback, then probes once to recover.
Fail-open telemetry. Every call that falls open reports itself to Elastly (fire and forget, never on your latency path), so an outage that hit your quote screen shows up in your dashboard.

Build a connector

To push your own ERP or storefront into Elastly, the SDK ships a connector runtime: implement a few functions that read your data, and define_connector runs the whole sync, with paging, checkpoints, retries, and write-back leases handled for you.

Build a connector

Feed your data in, apply approved prices back, in Python or any other language.

Versioning

The SDK’s major version is bound to the API version in the URL. Every 0.x and 1.x release talks to /api/v1, so an upgrade within a major is always safe. The source is on GitHub. It is generated, so file an issue rather than a pull request against generated code.

​Keys and scopes

​The one thing to get right: the decision id

​Price a line, with a fallback

​Typed errors

​Verify a webhook

​What the SDK handles for you

​Build a connector

Build a connector

​Versioning

Keys and scopes

The one thing to get right: the decision id

Price a line, with a fallback

Typed errors

Verify a webhook

What the SDK handles for you

Build a connector

Versioning