> ## Documentation Index
> Fetch the complete documentation index at: https://docs.blnkfinance.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Using the SDK
> Configure authentication, timeouts, retries, and logging for the Python SDK.
export const CtaCallout = props => {
const {title, buttonLabel, href, trackingEvent, buttonTarget, rel = "noopener noreferrer", children} = props;
const handleCtaClick = () => {
if (typeof window === "undefined" || !trackingEvent) {
return;
}
try {
window.dispatchEvent(new CustomEvent("blnk:docs-cta", {
detail: {
name: trackingEvent,
href
}
}));
} catch {}
try {
window.posthog?.capture?.(trackingEvent, {
href
});
} catch {}
const gaPayload = {
cta_href: href
};
try {
window.gtag?.("event", trackingEvent, gaPayload);
} catch {}
try {
window.dataLayer = window.dataLayer || [];
window.dataLayer.push({
event: trackingEvent,
...gaPayload
});
} catch {}
};
const isExternal = typeof href === "string" && (/^https?:\/\//i).test(href);
const target = buttonTarget ?? (isExternal ? "_blank" : undefined);
const linkRel = isExternal ? rel : undefined;
return ;
};
Configurable client options ship in v1.3.0. See the [Changelog](/changelog/blnk-py) before upgrading.
## Initialize the client
Your Blnk client is the single entry point to everything: ledgers, balances, transactions, webhooks, and more. Configure it once when your app starts, then use it everywhere.
```python blnk_client.py wrap theme={"system"}
import os
from blnk_sdk import BlnkClientOptions, blnk_init
blnk = blnk_init(
os.environ.get("BLNK_API_KEY", ""),
BlnkClientOptions(
base_url=os.environ.get("BLNK_BASE_URL", "http://localhost:5001"),
),
)
```
That's it. One import, one call, one client. From here you can create ledgers, move money, reconcile transactions, and manage your entire financial infrastructure.
```python create_ledger.py wrap theme={"system"}
from blnk_client import blnk
response = blnk.ledgers.create(
{
"name": "Customer Savings Account",
"meta_data": {
"project_owner": "YOUR_APP_NAME",
},
}
)
print("Ledger Created:", response.data)
```
Use a context manager when you want the underlying `requests.Session` closed automatically:
```python wrap theme={"system"}
from blnk_sdk import BlnkClientOptions, blnk_init
with blnk_init(api_key, BlnkClientOptions(base_url=base_url)) as blnk:
response = blnk.ledgers.create({"name": "Temporary ledger"})
```
***
## Authentication
`blnk_init` takes two arguments: an API key and a `BlnkClientOptions` object.
The options object must include `base_url`, the root URL of your Blnk Core instance. The SDK sends the API key on every request in the `X-Blnk-Key` header.
How you set the API key depends on whether Core runs in secure mode:
When `server.secure` is enabled, pass your API key as the first argument. Set `base_url` to the URL where Core is reachable.
```python wrap theme={"system"}
import os
from blnk_sdk import BlnkClientOptions, blnk_init
blnk = blnk_init(
os.environ.get("BLNK_API_KEY", ""),
BlnkClientOptions(
base_url=os.environ.get("BLNK_BASE_URL", "http://localhost:5001"),
),
)
```
When secure mode is off, pass an empty string as the first argument.
```python wrap theme={"system"}
from blnk_sdk import BlnkClientOptions, blnk_init
blnk = blnk_init(
"",
BlnkClientOptions(base_url="http://localhost:5001"),
)
```
Secure mode, master key, and server hardening.
Owner-scoped keys and permission limits.
***
## Timeouts and retries
When connections fail, Core restarts, or requests hang, the SDK handles it without blocking your app. Pass these parameters on `BlnkClientOptions`:
```python wrap theme={"system"}
from blnk_sdk import BlnkClientOptions, blnk_init
blnk = blnk_init(
api_key,
BlnkClientOptions(
base_url="http://localhost:5001",
timeout=30000,
retry_count=3,
retry_delay_ms=2000,
),
)
```
| Option | Type | Default | What it does for you |
| :--------------- | :---- | :------ | :----------------------------------------------------------------------------------------------------------- |
| `timeout` | `int` | `10000` | Milliseconds to wait before giving up on a request. Bump this for slow operations like bulk reconciliations. |
| `retry_count` | `int` | `1` | Total attempts including the first. `1` means one attempt, no retries. `3` means try up to 3 times. |
| `retry_delay_ms` | `int` | `2000` | Milliseconds between retries. Uses linear backoff. |
When to tune these:
* Keep defaults if you're making fast, local calls and want to fail fast.
* Increase `timeout` if you're running large batch requests that may take a while to complete synchronously.
* Increase `retry_count` if you're reading data across an unreliable network.
***
## Custom logger
By default, the SDK logs internal events through a built-in logger that writes to the console with `INFO:`, `ERROR:`, and `DEBUG:` prefixes.
Pass a custom logger to route these messages to your own logging system instead of the console.
```python wrap theme={"system"}
from blnk_sdk import BlnkClientOptions, CustomLogger, blnk_init
class AppLogger(CustomLogger):
def info(self, message, *meta):
app_logger.info(message, extra={"meta": meta})
def error(self, message, *meta):
app_logger.error(message, extra={"meta": meta})
blnk = blnk_init(
api_key,
BlnkClientOptions(
base_url="http://localhost:5001",
logger=AppLogger(),
),
)
```
Metadata passed to the logger is redacted. The SDK strips values for keys such as `api_key`, `authorization`, `token`, and `secret` before logging.
| Level | When the SDK calls it |
| :------ | :------------------------------------------------------------------------------------------ |
| `info` | Before a retry, or when a retryable `GET` failure will be retried |
| `error` | When a request times out, returns a non-retryable HTTP error, or fails with a network error |
```bash Example logs wrap theme={"system"}
INFO: Retrying request to transactions/txn_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94 { attempt: 2, maxAttempts: 3, delayMs: 2000 }
ERROR: Request timed out { endpoint: 'transactions/txn_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94', timeoutMs: 30000 }
ERROR: Request to transactions/txn_f482a1b3-6c2d-4e89-a17b-3d5e8f2a1c94 failed with status 404.
```
***
## Related docs
Install the SDK and create your first transaction.
ApiResponse checks and Core error bodies.
Python SDK releases and version history.
***
## Need help?
We are very happy to help you make the most of Blnk, regardless of whether it is your first time or you are switching from another tool.
To ask questions or discuss issues, please [contact us](mailto:support@blnkfinance.com) or [join our Discord community](https://discord.gg/7WNv94zPpx).
Sign up and manage your ledger with our back-office dashboard. You can invite teammates to collaborate and manage your ledger operations directly from the dashboard.