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<!-- source: en/_includes/flow/python/examples/static_table_join.md -->
# Static Table Join in YTsaurus Flow (Python)

This pipeline loads a static reference table into external state and enriches queue events by the shared key.

[Source code](https://github.com/ytsaurus/ytsaurus/tree/main/yt/yt/flow/examples/python/static_table_join)

## Pipeline structure {#structure}

- `reference_reader` reads the static table;
- `reference_loader` normalizes reference values and writes them to `/reference_state`;
- `event_reader` reads queue events;
- `enricher` performs a read-only lookup through the joiner named `/reference_state` and writes successful matches to `enriched`.

The manager and joiner point to the same dynamic state table. Their keys must match the computations' `group_by_schema`. See the [pipeline spec](https://github.com/ytsaurus/ytsaurus/tree/main/yt/yt/flow/examples/python/static_table_join/pipeline.yson).

## Load and join {#implementation}

The loader uses `ctx.external_state(...)` and persists the normalized value. The enricher uses `ctx.joined_external_state(...)`; when `normalized_name` is absent, it emits nothing.

```python
class ReferenceLoader(RowFunction):
    """Trims and lowercases the reference name, storing it in external state."""

    def on_message(self, message, output, ctx):
        name = message.payload["name"]
        normalized_name = name.strip().lower()

        state = ctx.external_state("/reference_state", message)
        builder = state.to_builder()
        builder.set("normalized_name", normalized_name)
        state.set(builder.finish())

```

```python
class Enricher(RowFunction):
    """Joins each event against the reference state and emits the enriched row."""

    def on_message(self, message, output, ctx):
        state = ctx.joined_external_state("/reference_state", message)
        normalized_name = state.get("normalized_name")
        if normalized_name is None:
            return

        builder = ctx.message_builder("enriched")
        builder.set("key", message.payload["key"])
        builder.set("name", normalized_name)
        output.add_message(builder.finish())

```

## See also

- [External State (Python)](https://ytsaurus.tech/docs/en/flow/python/external-state.md)
- [External State Join example](https://ytsaurus.tech/docs/en/flow/python/examples/external_state_join.md)
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