# Callback I

Sometimes you may be interested in an event taking place at a particular location during processing.

```python
import pyblish.api

def on_published(context):
  has_error = any(result["error"] is not None for result in context.data["results"])
  print("Publishing %s" % ("failed" if has_error else "finished"))

pyblish.api.register_callback("published", on_published)
```

This will cause `"Publishing finished"` or `"Publishing failed"` to be printed upon completed publishing, based on whether it completed successfully or not.

The arguments provided by the signal must match those in your callback. See [here](https://pyblish.gitbooks.io/api/content/pages/Events.html) for a complete list of signals emitted in Pyblish.

* [Events](https://pyblish.gitbooks.io/api/content/pages/Events.html)


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://learn.pyblish.com/20-callback-i.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.