Jupyter Storage Explorer launcher

Adds Storage Explorer to JupyterLab's launcher (section Other) and command palette. It opens Jupyter Storage Explorer in its own tab, with a kernel of its own that stops when the tab is closed.

The tab opens on the launcher's folder: the one JupyterLab's file browser showed when the launcher was opened (like the launcher's Notebook and Console items; open a new launcher after changing folder). From the command palette, it opens on the folder the file browser shows. When the page is reloaded, JupyterLab restores the tab and the explorer is shown again, from a new run of launch() in the same kernel.

pip install jupyter-storage-explorer-launcher

Install it in the environment of JupyterLab and of the default kernel (on JupyterHub, usually the single-user image), then restart JupyterLab. It installs jupyter-storage-explorer too.

What the tab shows is set by a file storage-explorer/launcher.py in a Jupyter configuration directory: its launch() function returns the widget. For example, for one user, ~/.jupyter/storage-explorer/launcher.py:

from jupyter_storage_explorer import StorageExplorer


def launch():
    return StorageExplorer(
        # "." is the folder the tab opens on (see above)
        filesystems={
            "Here": ".",
            "Data lake": "abfs://lake@myaccount.dfs.core.windows.net",
        },
        height="fill",  # as tall as the tab
    )

Administrators can put one in /etc/jupyter/storage-explorer/launcher.py (or <environment>/etc/jupyter/...) for everyone. The directories are searched in Jupyter's usual order (jupyter --paths, config section) and the first file found is used. Without one, the tab shows an explorer of the folder it opens on.

The file may also have a style() function returning CSS (without <style>), e.g. to customize the explorer's icons (see Customizing icons). It applies to the whole JupyterLab page while the tab is open:

def style():
    # The folders in the top folder as 🗃️ instead of 📁: hide the icon, show another
    return """
    .jse-browser [data-depth="1"] .jse-icon { font-size: 0; }
    .jse-browser [data-depth="1"] .jse-icon::before { font-size: 14px; content: "🗃️"; }
    """

Requires JupyterLab 4.