plot_kernel

05_kernel.ipynb

custom_kernel.png

custom_kernel_example.ipynb

plotkernel.py

from IPython.kernel.zmq.kernelbase import Kernel

import numpy as np
import matplotlib.pyplot as plt

from io import BytesIO
import urllib, base64

def _to_png(fig):
    """Return a base64-encoded PNG from a 
    matplotlib figure."""
    imgdata = BytesIO()
    fig.savefig(imgdata, format='png')
    imgdata.seek(0)
    return urllib.parse.quote(
        base64.b64encode(imgdata.getvalue()))

_numpy_namespace = {n: getattr(np, n) 
                    for n in dir(np)}

def _parse_function(code):
    """Return a NumPy function from a string 'y=f(x)'."""
    return lambda x: eval(code.split('=')[1].strip(),
                          _numpy_namespace, {'x': x})
    
class PlotKernel(Kernel):
    implementation = 'Plot'
    implementation_version = '1.0'
    language = 'no-op'
    language_version = '0.1'
    banner = "Simple plotting"

    def do_execute(self, code, silent,
                   store_history=True,
                   user_expressions=None,
                   allow_stdin=False):
        if not silent:
            fig = plt.figure(figsize=(6,4), dpi=100)
            x = np.linspace(-5., 5., 200)
            for line in code.split('\n'):
                f = _parse_function(line)
                y = f(x)
                plt.plot(x, y)
            plt.xlim(-5, 5)
            png = _to_png(fig)
            content = {
                'source': 'kernel',
                'data': {
                    'image/png': png,
                    'text/plain': str(len(png))
                },
                'metadata' : {
                      'image/png' : {
                        'width': 600,
                        'height': 400
                      }
                    }
            }
            self.send_response(self.iopub_socket,
                'stream', {'name': 'stdout', 'data': ''})
            self.send_response(self.iopub_socket,
                'display_data', content)

        return {'status': 'ok',
                'execution_count': self.execution_count,
                'payload': [],
                'user_expressions': {},
               }
               
    def do_complete(self, code, cursor_pos):
        return {'status': 'ok',
                'cursor_start': 0,
                'cursor_end': 0,
                'matches': []}

if __name__ == '__main__':
    from IPython.kernel.zmq.kernelapp import IPKernelApp
    IPKernelApp.launch_instance(kernel_class=PlotKernel)
    
    # ipython notebook --KernelManager.kernel_cmd="['python','-m','echokernel', '-f', '{connection_file}']"