[FIXED] How to reload a jupyter notebook after a kernel restart?

Issue

In a jupyter notebook I would like to define a function in python, which, when called, does the following:

• Gives out an alert to the user
• Restarts the notebook kernel
• Marks the executed cell as done (i.e. without a star, [ ])
• Focus is on the next cell

Or as an alternative:

• Gives out an alert to the user
• Restarts the notebook kernel
• Clears all the output of the entire notebook
• Focus is on the first cell again (like a F5 reload of the browser tab).

I have tried the following code

from IPython.display import display, HTML

def reload():
    display(HTML(
        '''
            <script>
                alert('This notebook needs to be restarted!');

                IPython.notebook.kernel.restart(); 
                IPython.display.clear_output();

                window.location.reload();

            </script>            
        '''
    ))
reload()

but it gives an error

AttributeError: 'function' object has no attribute 'clear_output'

despite this documentation.

When I remove the line

IPython.display.clear_output();

then the kernel is restarted, but I get 2(!) alerts and it looks like that the execution of the next cell is performed. Also, the cells are not cleared , the current cell still does have the star in the brackets ([*]).

How to do it correctly?

Solution

This code does what you described as the alternative option, with the addition of saving a checkpoint before reloading so the output stays cleared:

from IPython.display import Javascript, display


def reload():
    display(
        Javascript('''
            // clear all output (based on: https://stackoverflow.com/a/47315713/9504155)           
            // save a reference to the cell we're currently executing inside of,
            // to avoid clearing it later (which would remove this js)
            var this_cell = $(element).closest('.cell').data('cell');
            function clear_other_cells () {
                Jupyter.notebook.get_cells().forEach(function (cell) {
                    if (cell.cell_type === 'code' && cell !== this_cell) {
                        cell.clear_output();
                    }
                    Jupyter.notebook.set_dirty(true);
                });
            }

            if (Jupyter.notebook._fully_loaded) {
                // notebook has already been fully loaded, so clear now
                clear_other_cells();
            }

            // save checkpoint so output stays cleared after reload
            IPython.notebook.save_checkpoint();

            IPython.notebook.kernel.restart();

            alert('This notebook needs to be restarted!');
            window.location.reload(false);
        '''))

reload()

If you prefer the first option (without reloading the page, focusing on the next cell instead) just remove the lines for saving a checkpoint and reloading and use the IPython.display.clear_output() function after the JavaScript part to clear the current cell's output as well:

from IPython.display import Javascript, clear_output, display


def reload():
    display(
        Javascript('''
            // clear all output (based on: https://stackoverflow.com/a/47315713/9504155)           
            // save a reference to the cell we're currently executing inside of,
            // to avoid clearing it later (which would remove this js)
            var this_cell = $(element).closest('.cell').data('cell');
            function clear_other_cells () {
                Jupyter.notebook.get_cells().forEach(function (cell) {
                    if (cell.cell_type === 'code' && cell !== this_cell) {
                        cell.clear_output();
                    }
                    Jupyter.notebook.set_dirty(true);
                });
            }

            if (Jupyter.notebook._fully_loaded) {
                // notebook has already been fully loaded, so clear now
                clear_other_cells();
            }

            IPython.notebook.kernel.restart();

            alert('Notebook output cleared!');
        '''))
    clear_output()

IPython.display.clear_output(); was not working in your code because it was called in the HTML <script> tag as JavaScript code instead of in Python.

Answered By - Jonathan Feenstra