> ## Documentation Index
> Fetch the complete documentation index at: https://elastly.io/docs/llms.txt
> Use this file to discover all available pages before exploring further.

# Python SDK

> Price lines with a hard deadline and a fallback, verify webhooks, and sync a connector, from Python.

The `elastly` package is the supported way to call Elastly from Python. The request and response types
are generated from the same [OpenAPI contract](/docs/api/overview) 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.

```bash theme={null}
pip install elastly
```

Python 3.9 or later.

## Keys and scopes

Create API keys under [Settings → API keys](https://app.elastly.io/settings). 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` |

```python theme={null}
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:

```python theme={null}
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:

```python theme={null}
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:

```python theme={null}
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:

```python theme={null}
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

```python theme={null}
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.

<Card title="Build a connector" icon="wrench" href="/docs/sdks/build-a-connector">
  Feed your data in, apply approved prices back, in Python or any other language.
</Card>

## 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](https://github.com/elastly/elastly-python). It is generated, so file an issue
rather than a pull request against generated code.