---
title: add_custom_attribute (Python agent API)
source: https://docs.newrelic.com/docs/apm/agents/python-agent/python-agent-api/addcustomattribute-python-agent-api
---

## Syntax

```py
newrelic.agent.add_custom_attribute(key, value)
```

Adds a [custom attribute](https://docs.newrelic.com/docs/data-apis/custom-data/custom-events/collect-custom-attributes/) to a transaction.

## Description

This call records a [custom attribute](https://docs.newrelic.com/docs/new-relic-solutions/get-started/glossary/#attribute) (a key/value pair attached to your [transaction](https://docs.newrelic.com/docs/new-relic-solutions/get-started/glossary/#transaction)).

Attributes may be found in APM if the transaction is associated with an error or if a transaction trace is generated for that transaction. Attributes can also be found and queried in the New Relic UI.

> #### ⚠️ IMPORTANT
>
> Before you create custom attributes, review our list of [reserved terms used by NRQL](https://docs.newrelic.com/docs/data-apis/custom-data/custom-events/data-requirements-limits-custom-event-data/#reserved-words).

## Attributes

| Attribute                                       | Description                                                                                               |
| ----------------------------------------------- | --------------------------------------------------------------------------------------------------------- |
| `key` _string_                                  | Required. The key name. Only the first 255 characters are retained.                                       |
| `value` _string_, _integer_, _float_, _boolean_ | Required. The string value to add to the current transaction. Only the first 255 characters are retained. |

## Return values

Returns `True` if attribute was added successfully. 

## Examples

### Adding custom attributes to background task [#custom-attribute-example]

An example of adding custom attributes to a [background task](https://docs.newrelic.com/docs/agents/python-agent/python-agent-api/background_task):

```py
@newrelic.agent.background_task()
def send_request(): 
    response = requests.post('http://URL_path', headers=headers, data=data) 
    newrelic.agent.add_custom_attribute('url_path_status_code', response.status_code)
```

### Using custom attributes to troubleshoot [#attribute-troubleshooting]

You can also use custom attributes to troubleshoot performance issues. For example, you might see occasional slow response times from a pool of memcache instances, but you don't know what instance is causing the problem. You might add an attribute to the transaction indicating the server, like so:

```py
# Set server_ip to be the current server processing the transaction

newrelic.agent.add_custom_attribute("memcache_query_frontend_lookup", server_ip)
```