# Customizing with Lifecycle Hooks

## Background

{% content-ref url="../../../../core-concepts/agent/lifecycle-hooks" %}
[lifecycle-hooks](https://docs.stoobly.com/core-concepts/agent/lifecycle-hooks)
{% endcontent-ref %}

## Writing a Lifecycle Hooks Script

1. Write a Python script (e.g. lifecycle\_hooks.py)
2. In this script, define the lifecycle events to hook into
3. Define what kind of behavior to execute for each of those events

Below is a sample script that prints some strings during two lifecycle events.

{% hint style="warning" %}
Manipulating the **context** object will affect the behaviour of the request interception.
{% endhint %}

```python
from stoobly_agent.app.proxy.replay.context import ReplayContext

def handle_before_replay(context: ReplayContext):
    print('Before replay!')

```

After a request gets intercepted, the string `"Before replay!"` will be printed.

## Enabling Lifecycle Hook Script Use

Pass the path to the lifecycle hooks scripts using the `--lifecycle-hooks-path` option:

```bash
stoobly-agent run --lifecycle-hooks-path ~/path-to-file/lifecycle_hooks.py
```

## Example

```python
from stoobly_agent.app.proxy.replay.context import ReplayContext
from stoobly_agent.config.constants import record_policy, replay_policy

def handle_before_replay(context: ReplayContext):
    intercept_settings = context.intercept_settings
    flow = context.flow
    headers = flow.request
    request = request.headers
    
    is_overwriting = intercept_settings.policy == record_policy.OVERWRITE
    if is_overwriting:
        # Handle setting credentials here
        # e.g. headers['authorization'] = '<TOKEN>'
        pass
```