# Python Versions and Packages

The project settings file configures the project for a specific version of Python. This file is named `yourprojectname.celbridge`, and is visible in the explorer panel.

For example, this screenshot shows the project settings file for a project named **sample-project-01**:

```{image} /02_setup/images/project_settings_explorer_panel.png
:alt: Screenshot showing .celbridge configuration file in the file explorer panel
:width: 50%
```

## Python version

The `project` section of the project settings file uses key `requires-python` to declare the Python version for the project. For example, this declares Python version **3.12** for a project:

```
[project]
requires-python = "3.12"
```

If your project requires a specific version of Python, then it's this project setting you need to ensure specifies that version.

:::{note}
Every project **must** have a `[project]` section, with a `requires-python` key that declares the required Python language version.

When you create a new Celbridge project an up-to-date version of Python will automatically be declared in the project settings file created with the project.
:::

## Python Packages

Additionally, you can specific Python (PyPi) packages to be automatically loaded through the project settings file.

For example, let's add the data analysis library [Pandas] to our Celbridge project.

1. Open the `.celbridge` project settings file:
   : - double-click it in the explorer panel.
2. Add `"pandas"` to the `dependencies` key in the `[project]` section.
   : - (create a dependencies key if one isn't already present)
     - ensure you wrap double-quotes around the package name.

```
[project]
requires-python = "3.12"
dependencies = ["pandas"]
```

```{image} /02_setup/images/dependencies_pandas.png
:alt: Screenshot showing Python version and extensions in .celbridge configuration
:  file
```

3. After a second or two Celbridge will detect you have changed the project settings file, and in the **Console** you'll be offered a button to `Reload project`

```{image} /02_setup/images/reload_project.png
:alt: Screenshot showing button in Console panel allowing user to to Reload Project
```

4. The console window will show Pandas being installed, after the Python virtual environemnt has been set up (give it a few seconds!).

You can specify multiple packages by declaring a comma-separate list of them in the `dependencies` key. For example, here we specify both the `"pandas"` and `"numpy"` packages:

```
[project]
requires-python = "3.12"
dependencies = ["pandas", "numpy"]
```

For a list of Python packages visit [Pypi]

[pandas]: https://pandas.pydata.org/
[pypi]: https://pypi.org/