The IPython Protocol

Frontends and Kernels

The logistics of this presentation¶

What is IPython?¶

The punchline...¶

"Why should I care?"

Implement one piece - and get the others for free.

(free as in BSD)

This talk¶

Analogy (imperfect, but useful)¶

<tr><th>The Web</th><th width=400px></th><th>IPython</th></tr>
<tr><td>
    Browser
    <br>
    ![](images/nextstation.jpg)
    </td>

    <td width=400px></td>
    <td>
    Client
    <br>
    ![](images/computer.png)
    </td>
</tr>

<tr><td>
<br>
    <h3>speaks **HTTP** with</h3>
      <br>

    <br>

    </td>

    <td width=400px></td>
    <td>
            <br>

    <h3>speaks "ICCP" with</h3>
            <br>

    </td>
</tr>

<tr><td>
    Webserver
    <br>
    ![](images/next.jpg)
    </td>

    <td width=400px></td>
    <td>
    Kernel
    <br>
    ![](images/pdp12.jpg)
    </td>
</tr>

ICCP?¶

Interactive Computing Communication Protocol

I wanted "IPython Protocol"

• but IP was already taken :\

"Interactive Computing Protocol"

• also taken ("Internet Cache Protocol", RFCs

2186 and 2187)

Kernel¶

Computational Engine¶

- accepts messages

- performs actions

- sends out results

One-to-Many (Kernel to Clients)¶

Anatomy of a Message¶

In brief, read the messaging spec for more details.

Essential fields:

header:
    msg_id:
    msg_type: execute_request, execute_reply, object_info_request,
    complete_request, complete_reply, history_request, ...

parent_header: (see above)

content: structure depends on message type

    example: `execute_request`
        - `code` (str)
        - `silent` (bool)
        - `store_history` (bool)

    example: `execute_reply`
        - `status` ('ok', 'error', or 'abort')
        - `execution count` (prompt numbers)

Client¶

- connects to exactly one kernel


- send messages to kernel based on user actions


- displays kernel messages when appropriate

Why have many clients?¶

Differences in

• multiline editing
  • qtconsole
  • vim-ipython
  • notebook
• display capabilities
  • images in qtconsole
  • images, video, javascript in notebook
• persistence
  • no save and rerun in console, qtconsole
  • .ipynb files for notebook, EIN
  • files for vim-ipython
• user interface

  I have a serious illness: chronic CLI. It's terminal.

  — Paul Ivanov (@ivanov) May 3, 2014

• client-side requirements
  • python for console, qtconsle, vim-ipython, bipython
  • modern webbrowser for notebook
• interactivity (bipython)

Clients¶

ship with ipython:¶

ipython qtconsole - the original decoupling, uses Qt4

ipython console - terminal version, decoupled

• (different from the classic single process ipython)

both of these actually start a kernel and a client, pass --existing flag to not start a new kernel and instead simply connect to one that already exists ipython notebook ♦ ♦ - more on this later

3rd party¶

vim-ipython

bipython

EIN - Emacs IPython Notebook (OOS)

vim-ipython¶

vim plugin first written during the sprints at SciPy 2011

demo #1 demo #2

Live demo?¶

PSA: vim-ipython common problem (e.g. OS X)¶

Vim needs to be compiled with Python support (vim --version | grep +python) AND the Python linked must have IPython with ZeroMQ support

HOWEVER: the Python linked does not need to be your preferred Python.

Solution: either install IPython and PyZMQ into system Python, or compile vim against a Python which has IPython and PyZMQ (Python that comes with Anaconda, for example)

bipython¶

ripped out the messaging code from vim-ipython,

and slapped them on top of bpython's urwid interface

...in 2 days.

Live Demo?¶

Embed is you friend!¶

In any Python code you have lying around, do this:

import IPython; IPython.embed_kernel()

When that code runs, it will prompt something like this:

NOTE: When using the `ipython kernel` entry point, Ctrl-C will not work.

To exit, you will have to explicitly quit this process, by either sending
"quit" from a client, or using Ctrl-\ in UNIX-like environments.

To read more about this, see https://github.com/ipython/ipython/issues/2049


To connect another client to this kernel, use:
    --existing kernel-5979.json

(demo if time permits)

Take away for clients¶

You favorite tool can talk (bi-directionally) to Python!

Bonus slides¶

Lies¶

ICCP over zermoq happens over multiple channels (3) not just one. - stdin - Shell ( action requests: execution, object introspection, code completion ) - IOPub ( "broadcast channel" )

What about the notebook? (analogy)¶

see sequence diagram