Update an entity.

## Explore further


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

- [Entities, Properties, and Keys](https://docs.cloud.google.com/datastore/docs/concepts/entities)

## Code sample

### C#


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


For more information, see the
[Datastore mode C# API
reference documentation](https://cloud.google.com/dotnet/docs/reference/Google.Cloud.Datastore.V1/latest).


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    _sampleTask["priority"] = 5;
    _db.Update(_sampleTask);

### Go


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


For more information, see the
[Datastore mode Go API
reference documentation](https://cloud.google.com/go/docs/reference/cloud.google.com/go/datastore/latest).


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    taskKey := datastore.NameKey("Task", "sampleTask", nil)
    tx, err := client.NewTransaction(ctx)
    if err != nil {
    	log.Fatalf("client.NewTransaction: %v", err)
    }
    var task Task
    if err := tx.Get(taskKey, &task); err != nil {
    	log.Fatalf("tx.Get: %v", err)
    }
    task.Priority = 5
    if _, err := tx.Put(taskKey, &task); err != nil {
    	log.Fatalf("tx.Put: %v", err)
    }
    if _, err := tx.Commit(); err != nil {
    	log.Fatalf("tx.Commit: %v", err)
    }

### Java


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


For more information, see the
[Datastore mode Java API
reference documentation](https://cloud.google.com/java/docs/reference/google-cloud-datastore/latest/history).


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    Entity task;
    Transaction txn = datastore.newTransaction();
    try {
      task = Entity.newBuilder(txn.get(taskKey)).set("priority", 5).build();
      txn.put(task);
      txn.commit();
    } finally {
      if (txn.isActive()) {
        txn.rollback();
      }
    }

### PHP


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


For more information, see the
[Datastore mode PHP API
reference documentation](https://googleapis.github.io/google-cloud-php/#/docs/cloud-datastore/latest).


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    $transaction = $datastore->transaction();
    $key = $datastore->key('Task', 'sampleTask');
    $task = $transaction->lookup($key);
    $task['priority'] = 5;
    $transaction->update($task);
    $transaction->commit();

### Python


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


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


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

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

    # For help authenticating your client, visit
    # https://cloud.google.com/docs/authentication/getting-started
    client = https://docs.cloud.google.com/python/docs/reference/datastore/latest.https://docs.cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html()

    with client.https://docs.cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_transaction():
        key = client.https://docs.cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_key("Task", "sampleTask")
        task = client.https://docs.cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_get(key)

        task["done"] = True

        client.https://docs.cloud.google.com/python/docs/reference/datastore/latest/google.cloud.datastore.client.Client.html#google_cloud_datastore_client_Client_put(task)

### Ruby


To learn how to install and use the client library for Datastore mode, see
[Datastore mode client libraries](https://docs.cloud.google.com/datastore/docs/reference/libraries).


For more information, see the
[Datastore mode Ruby API
reference documentation](https://docs.cloud.google.com/ruby/docs/reference/google-cloud-datastore/latest).


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

[Set up authentication for a local development environment](https://docs.cloud.google.com/docs/authentication/set-up-adc-local-dev-environment).

    # task_name = "sampleTask"
    datastore.transaction do |_tx|
      task = datastore.find "Task", task_name
      task["priority"] = 5
      datastore.save task
    end

## 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=datastore).