Edit IPython cell in an external editor

This is what I came up with. I added 2 shortcuts:

• 'g' to launch gvim with the content of the current cell (you can replace gvim with whatever text editor you like).
• 'u' to update the content of the current cell with what was saved by gvim.

So, when you want to edit the cell with your preferred editor, hit 'g', make the changes you want to the cell, save the file in your editor (and quit), then hit 'u'.

Just execute this cell to enable these features:

%%javascript

IPython.keyboard_manager.command_shortcuts.add_shortcut('g', {
    handler : function (event) {
        var input = IPython.notebook.get_selected_cell().get_text();
        var cmd = "f = open('.toto.py', 'w');f.close()";
        if (input != "") {
            cmd = '%%writefile .toto.py\n' + input;
        }
        IPython.notebook.kernel.execute(cmd);
        cmd = "import os;os.system('gvim .toto.py')";
        IPython.notebook.kernel.execute(cmd);
        return false;
    }}
);

IPython.keyboard_manager.command_shortcuts.add_shortcut('u', {
    handler : function (event) {
        function handle_output(msg) {
            var ret = msg.content.text;
            IPython.notebook.get_selected_cell().set_text(ret);
        }
        var callback = {'output': handle_output};
        var cmd = "f = open('.toto.py', 'r');print(f.read())";
        IPython.notebook.kernel.execute(cmd, {iopub: callback}, {silent: false});
        return false;
    }}
);

For people who find this question who are using the IPython terminal application, there is a keyboard shortcut built in which launches $EDITOR with the contents of the current cell. Saving and exiting the editor replaces (but does not yet execute) the contents of the cell with that of the saved file.

The default keyboard shortcut is the F2 key. This corresponds to the IPython setting IPython.terminal.shortcuts.open_input_in_editor.

Building off of the accepted answer by @david-brochart, I've taken his code and wrapped it up into a magic function so now I only need to run the line magic%gvim in a notebook in order to enable editing any cell's contents via Gvim for the entire notebook (and I can reuse the same line magic in any other notebook running on my system).

If you'd like to do something similar, just create a file named something like my_magic_functions.py inside your ipython startup folder (your ipython startup path is likely similar to ~/.ipython/profile_default/startup) and then put the following code inside that file (and save it):

import IPython.core.magic as ipym
from IPython import get_ipython

@ipym.magics_class
class MareBearMagics(ipym.Magics):
    @ipym.line_magic
    def gvim(self, line):
        cell_text = """
IPython.keyboard_manager.command_shortcuts.add_shortcut('g', {
    handler : function (event) {
        var input = IPython.notebook.get_selected_cell().get_text();
        var cmd = "f = open('.toto.py', 'w');f.close()";
        if (input != "") {
            cmd = '%%writefile .toto.py\\n' + input;
        }
        IPython.notebook.kernel.execute(cmd);
        cmd = "import os;os.system('gvim .toto.py')";
        IPython.notebook.kernel.execute(cmd);
        return false;
    }}
);

IPython.keyboard_manager.command_shortcuts.add_shortcut('u', {
    handler : function (event) {
        function handle_output(msg) {
            var ret = msg.content.text;
            IPython.notebook.get_selected_cell().set_text(ret);
        }
        var callback = {'output': handle_output};
        var cmd = "f = open('.toto.py', 'r');print(f.read())";
        IPython.notebook.kernel.execute(cmd, {iopub: callback}, {silent: false});
        return false;
    }}
);
        """
        ipython = get_ipython()
        ipython.run_cell_magic(
            magic_name='javascript', line=None, cell=cell_text)
        print("Cell contents can now be edited via Gvim. From command mode "
              "use 'g' to open current cell contents in Gvim. After ':wq' "
              "from Gvim, use 'u' in command mode to update cell contents.")


if __name__ == '__main__':
    get_ipython().register_magics(MareBearMagics)

Now start up your Jupyter notebook kernel, and you should be able to type %gvim% into a cell (and you can use auto-completion to find the new magic command) and then run the cell to enable editing the notebook's cell contents in Gvim. You'll receive an output message that lets you know the magic command took effect:

Cell contents can now be edited via Gvim. From command mode use 'g' to open current cell contents in Gvim. After ':wq' from Gvim, use 'u' in command mode to update cell contents.

Thanks to the folks in this stackoverflow question and these as well for giving me the ingredients to pull this together. :-)

• How to run an IPython magic from a script (or timing a Python script)
• How do I define custom magics in jupyter?