Work with earthquake metadata¶

These examples continue from the Item created in the tutorial.

Update or remove one field¶

earthquake = EarthquakeExtension.ext(item)
earthquake.depth = 9.2
earthquake.felt = None
assert "eq:felt" not in item.properties

ext(item) requires the extension to be declared already. Use add_if_missing=True when first attaching it. Assigning None removes a field, including fields that the specification describes as required.

apply() sets every supported field. Omitted optional arguments become None and remove existing values. Use property setters when you want to preserve other fields.

Read and override asset fields¶

asset = pystac.Asset(href="https://example.org/event.json", media_type="application/json")
item.add_asset("event", asset)
asset_earthquake = EarthquakeExtension.ext(asset)
assert asset_earthquake.magnitude == earthquake.magnitude
asset_earthquake.depth = 7.5
assert asset.extra_fields["eq:depth"] == 7.5
assert earthquake.depth == 9.2

Attach an asset to its owner before wrapping it. An Item asset reads missing fields from its owner's properties; writes affect the asset only. Removing an asset override exposes the Item value again. Collection assets have no equivalent fallback to Collection properties.

Use Collection item asset definitions¶

For an existing pystac.Collection with item asset definitions, retrieve the definition from collection.item_assets, then call EarthquakeExtension.ext(definition, add_if_missing=True). This declares the extension on the owning Collection and writes fields to the definition's properties.

The wrapper accepts Items, Assets, and ItemAssetDefinitions. It does not accept a Collection directly or provide a Collection summaries API.

Add a source link¶

Use ordinary PySTAC links for the specification's source relation:

item.add_link(
    pystac.Link(
        rel="source",
        target="https://example.org/events/event-001",
        media_type="text/html",
        extra_fields={"source": "example-network"},
    )
)

Keep the link's source aligned with a source record's name. Source links are not created by apply(). See the upstream relation types for the convention.