List datasets, filtering by labels.

## Explore further


For detailed documentation that includes this code sample, see the following:

- [Filtering resources using labels](https://docs.cloud.google.com/bigquery/docs/filtering-labels)

## Code sample

### Go


Before trying this sample, follow the Go setup instructions in the
[BigQuery quickstart using
client libraries](https://docs.cloud.google.com/bigquery/docs/quickstarts/quickstart-client-libraries).


For more information, see the
[BigQuery Go API
reference documentation](https://godoc.org/cloud.google.com/go/bigquery).


To authenticate to BigQuery, set up Application Default Credentials.
For more information, see

[Set up authentication for client libraries](https://docs.cloud.google.com/bigquery/docs/authentication#client-libs).

    import (
    	"context"
    	"fmt"
    	"io"

    	"cloud.google.com/go/bigquery"
    	"google.golang.org/api/iterator"
    )

    // listDatasetsByLabel demonstrates walking the collection of datasets in a project, and
    // filtering that list to a subset that has specific label metadata.
    func listDatasetsByLabel(w io.Writer, projectID string) error {
    	// projectID := "my-project-id"
    	ctx := context.Background()
    	client, err := bigquery.NewClient(ctx, projectID)
    	if err != nil {
    		return fmt.Errorf("bigquery.NewClient: %w", err)
    	}
    	defer client.Close()

    	it := client.https://docs.cloud.google.com/go/docs/reference/cloud.google.com/go/bigquery/latest/index.html#cloud_google_com_go_bigquery_Client_Datasets(ctx)
    	it.https://docs.cloud.google.com/go/docs/reference/cloud.google.com/go/bigquery/latest/migration/apiv2alpha/migrationpb.html#cloud_google_com_go_bigquery_migration_apiv2alpha_migrationpb_Filter = "labels.color:green"
    	for {
    		dataset, err := it.Next()
    		if err == iterator.Done {
    			break
    		}
    		if err != nil {
    			return err
    		}
    		fmt.Fprintf(w, "dataset: %s\n", dataset.DatasetID)
    	}
    	return nil
    }

### Java


Before trying this sample, follow the Java setup instructions in the
[BigQuery quickstart using
client libraries](https://docs.cloud.google.com/bigquery/docs/quickstarts/quickstart-client-libraries).


For more information, see the
[BigQuery Java API
reference documentation](https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/overview).


To authenticate to BigQuery, set up Application Default Credentials.
For more information, see

[Set up authentication for client libraries](https://docs.cloud.google.com/bigquery/docs/authentication#client-libs).

    import com.google.api.gax.paging.https://docs.cloud.google.com/java/docs/reference/gax/latest/com.google.api.gax.paging.Page.html;
    import com.google.cloud.bigquery.https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQuery.html;
    import com.google.cloud.bigquery.https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQueryException.html;
    import com.google.cloud.bigquery.https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQueryOptions.html;
    import com.google.cloud.bigquery.https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.Dataset.html;

    // Sample to get list of datasets by label
    public class ListDatasetsByLabel {

      public static void main(String[] args) {
        // TODO(developer): Replace these variables before running the sample.
        String projectId = "MY_PROJECT_ID";
        String filter = "MY_LABEL_FILTER";
        listDatasetsByLabel(projectId, filter);
      }

      public static void listDatasetsByLabel(String projectId, String filter) {
        try {
          // Initialize client that will be used to send requests. This client only needs to be created
          // once, and can be reused for multiple requests.
          https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQuery.html bigquery = https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQueryOptions.html.getDefaultInstance().getService();

          Page<Dataset> datasets =
              bigquery.https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQuery.html#com_google_cloud_bigquery_BigQuery_listDatasets_com_google_cloud_bigquery_BigQuery_DatasetListOption____(
                  projectId,
                  BigQuery.DatasetListOption.pageSize(100),
                  BigQuery.DatasetListOption.labelFilter(filter)); // "labels.color:green"
          if (datasets == null) {
            System.out.println("Dataset does not contain any models");
            return;
          }
          datasets
              .iterateAll()
              .forEach(
                  dataset -> System.out.printf("Success! Dataset ID: %s ", dataset.getDatasetId()));
        } catch (https://docs.cloud.google.com/java/docs/reference/google-cloud-bigquery/latest/com.google.cloud.bigquery.BigQueryException.html e) {
          System.out.println("Project does not contain any datasets \n" + e.toString());
        }
      }
    }

### Python


Before trying this sample, follow the Python setup instructions in the
[BigQuery quickstart using
client libraries](https://docs.cloud.google.com/bigquery/docs/quickstarts/quickstart-client-libraries).


For more information, see the
[BigQuery Python API
reference documentation](https://docs.cloud.google.com/python/docs/reference/bigquery/latest).


To authenticate to BigQuery, set up Application Default Credentials.
For more information, see

[Set up authentication for client libraries](https://docs.cloud.google.com/bigquery/docs/authentication#client-libs).


    from google.cloud import https://docs.cloud.google.com/python/docs/reference/bigquery/latest

    # Construct a BigQuery client object.
    client = https://docs.cloud.google.com/python/docs/reference/bigquery/latest.https://docs.cloud.google.com/python/docs/reference/bigquery/latest/google.cloud.bigquery.client.Client.html()

    label_filter = "labels.color:green"
    datasets = list(client.https://docs.cloud.google.com/python/docs/reference/bigquery/latest/google.cloud.bigquery.client.Client.html#google_cloud_bigquery_client_Client_list_datasets(filter=label_filter))  # Make an API request.

    if datasets:
        print("Datasets filtered by {}:".format(label_filter))
        for dataset in datasets:
            print("\t{}.{}".format(dataset.project, dataset.dataset_id))
    else:
        print("No datasets found with this filter.")

## What's next


To search and filter code samples for other Google Cloud products, see the
[Google Cloud sample browser](https://docs.cloud.google.com/docs/samples?product=bigquery).