Source: https://databento.com/docs/api-live/client/subscribe


### Live.subscribe

Add a new subscription to the session.
All subscriptions must be for the same `dataset`.
The returned integer is the `subscription_id` which will match the id used by the gateway when acknowledging the subscription.

Supports multiple subscriptions for different schemas, which enables rich data streams containing mixed record types.

Specify an optional `start` time for [intraday replay](https://databento.com/docs/api-live/basics/intraday-replay.md) with subscriptions made before starting the session.

Please note there is no unsubscribe method.
Subscriptions end when the client disconnects or by calling [Live.stop](https://databento.com/docs/api-live/client/stop.md) or [Live.terminate](https://databento.com/docs/api-live/client/terminate.md)

#### API method

```python
Live.subscribe(
    dataset: Dataset | str,
    schema: Schema | str,
    symbols: Iterable[str | int] | str | int = "ALL_SYMBOLS",
    stype_in: SType | str = "raw_symbol",
    start: pd.Timestamp | datetime | date | str | int | None = None,
    snapshot: bool = False,
) -> int
```

#### Parameters

| Parameter | Type | Required | Description |
| `dataset` | Dataset or str | required | The [dataset](https://databento.com/docs/api-historical/basics/datasets.md) code (string identifier). Must be one of the values from [list\_datasets](https://databento.com/docs/api-historical/metadata/metadata-list-datasets.md). |
| `schema` | Schema or str | required | The data record [schema](https://databento.com/docs/schemas/whats-a-schema.md). Must be one of the values from [list\_schemas](https://databento.com/docs/api-historical/metadata/metadata-list-schemas.md). |
| `symbols` | Iterable[str \ | int] or str or int | optional | The product symbols to subscribe to. If `'ALL_SYMBOLS'` then will select **all** symbols. |
| `stype_in` | SType or str, default 'raw_symbol' | optional | The [symbology type](https://databento.com/docs/api-historical/basics/symbology.md) of input `symbols`. Must be one of 'raw_symbol', 'instrument_id', 'parent', or 'continuous'. |
| `start` | pd.Timestamp, datetime, date, str or int | optional | The inclusive start of subscription replay. Filters on `ts_event` except for the CBBO and BBO schemas, which filter on `ts_recv`. Takes [pd.Timestamp](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Timestamp.html), [Python datetime](https://docs.python.org/3/library/datetime.html#datetime-objects), [Python date](https://docs.python.org/3/library/datetime.html#date-objects), [ISO 8601](https://www.iso.org/iso-8601-date-and-time-format.html) string, or [UNIX timestamp](https://en.wikipedia.org/wiki/Unix_time) in nanoseconds. Assumes UTC as timezone unless otherwise specified. Must be within the last 24 hours. Pass `0` to request all available data. Cannot be specified after the [session](https://databento.com/docs/api-live/basics/sessions.md) is [started](https://databento.com/docs/api-live/client/start.md). |
| `snapshot` | bool, default False | optional | Request subscription with [snapshot](https://databento.com/docs/conventions/mbo-snapshot.md). Only supported with `mbo` schema. Defaults to `False`. Conflicts with the `start` parameter. |

#### Example usage

```python
import databento as db

# Create a live client
client = db.Live(key="$YOUR_API_KEY")

# Subscribe to the trades schema for all ES futures
client.subscribe(
    dataset="GLBX.MDP3",
    schema="trades",
    stype_in="parent",
    symbols="ES.FUT",
)
```