# AxiniteArgs and the Body Class

In this guide, you'll learn about:

* the `AxiniteArgs` class and how to use it
* the `Body` class and how it differs from `axinite`'s standard `Body` class

## What are `AxiniteArgs`?

The `AxiniteArgs` class packages all the data from an Axinite file into one class. It has lots of attributes that can be used to keep track of various simulation parameters.

```python
args.name: str
args.delta: np.float64
args.limit: np.float64
args.action: function
args.t: np.float64
args.bodies: list<axtools.Body>
args.radius_multiplier: float or int
args.rate: float or int
args.retain: int
args.modifier: function
args.backend: function
```

The class also comes with an `unpack` function:

```python
*args.unpack()
```

{% hint style="warning" %}
Remember to unpack the tuple result with a `*`.
{% endhint %}

which can be used to easily supply the args to the `ax.load` function.

### Setting the Limit and Delta

When setting limits and deltas, don't use:

```python
args.delta = delta
args.limit = limit
```

Instead of setting the delta and limit attributes, use the included methods to change them:

```python
args.set_delta(delta)
args.set_limit(limit)
```

To avoid errors during loading.

## The `Body` Class

Although `axinite` comes with a `Body` class already, `axtools` contains an expanded one with more attributes, such as:

```python
body.mass: np.float64
body.r(n): np.ndarray
body.v(n): np.ndarray
body.name: str
body.radius: np.float64
body.color: str
body.light: bool
body.retain: int
body.radius_multiplier: int or float
body.rs: np.ndarray
body.vs: np.ndarray
```

The `axtools.Body` class can also take the place of an `axinite.Body`. You can create one with:

```python
body = axtools.Body("name", mass, limit, delta, position=[...], velocity=[..], color="color", light=False, retain=200, radius_multiplier=2)
```


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