# How to: Trace a function or script

The best way to use Kolo today is by using the [KoloMiddleware in a Django project](trace-django-requests). But, if you're not using Django, or want to trace a specific Python function or script, this guide walks through how to do that with `kolo.enable` and `kolo run`



#### with kolo.enable():
You can use `kolo.enable` as a context manager:

```python
import kolo


def fibonacci(n):
    if n == 0:
        return 0
    if n == 1:
        return 1
    return fibonacci(n - 1) + fibonacci(n - 2)


if __name__ == "__main__":
    with kolo.enable():
        print(fibonacci(6))
```

Kolo's tracing hooks into function calls and returns, not individual line executions. So for example in the code blow, Kolo will only trace the `fibonacci` call and return in the `with` block:

````python
def foo():
    with kolo.enable():
        b = 1 + 2
        f = fibonacci(5)
        return b + f
````

#### @kolo.enable()
You can also use `kolo.enable` as a decorator:

```python
import kolo


@kolo.enable
def fibonacci(n):
    if n == 0:
        return 0
    if n == 1:
        return 1
    return fibonacci(n - 1) + fibonacci(n - 2)
```

Kolo will now trace the `fibonacci` function whenever it is called in your program.

```{note}
`kolo.enable` can be nested arbitrarily. The outermost call will be used to generate the trace.
```

If you want to customise Kolo's behaviour while using `kolo.enable`, you can pass a `config` dictionary:

```python
config = {
    "filters": {
        "include_frames": ["include_path", "/more/data/to/include"],
        "ignore_frames": ["ignore_path"],
    },
}

with kolo.enable(config):
    ...


@kolo.enable(config=config)
def example():
    ...
```

For more information about including and ignoring frames, see [config.toml](../reference/config).

## kolo run

`kolo run` allows you to analyse your program from start to finish.

### Basic usage

Use `kolo run` to run your python script:

```bash
$ kolo run python example.py
```

Once your program exits you can see the trace in the Kolo web app at `http://localhost:8000/_kolo/` or in the [Kolo VSCode extension](vscode).

### Tests

`kolo run` can also be used with `unittest` or `pytest` to analyse the execution of your tests. For tests, we recommend using the `--one-trace-per-test` flag so that you get many small traces instead of one giant trace.

Examples:

```bash
$ kolo run --one-trace-per-test python manage.py test
$ kolo run --one-trace-per-test pytest
$ kolo run --one-trace-per-test unittest
```

### Limitations

If your program uses subprocesses or threading, `kolo run` is unable to analyse this code automatically.

```{note}
To trace Django requests, always use [`KoloMiddleware`](../howto/trace-django-requests.md) instead of `kolo run`
```




<!-- Todo: mention here to not use kolo with rusnerver. -->