This documentation covers IPython versions 6.0 and higher. Beginning with version 6.0, IPython stopped supporting compatibility with Python versions lower than 3.3 including all versions of Python 2.7.
If you are looking for an IPython version compatible with Python 2.7, please use the IPython 5.x LTS release and refer to its documentation (LTS is the long term support release).
Defining custom magics¶
There are two main ways to define your own magic functions: from standalone
functions and by inheriting from a base class provided by IPython:
IPython.core.magic.Magics. Below we show code you can place in a file
that you load from your configuration, such as any file in the
subdirectory of your default IPython profile.
First, let us see the simplest case. The following shows how to create a line magic, a cell one and one that works in both modes, using just plain functions:
from IPython.core.magic import (register_line_magic, register_cell_magic, register_line_cell_magic) @register_line_magic def lmagic(line): "my line magic" return line @register_cell_magic def cmagic(line, cell): "my cell magic" return line, cell @register_line_cell_magic def lcmagic(line, cell=None): "Magic that works both as %lcmagic and as %%lcmagic" if cell is None: print("Called as line magic") return line else: print("Called as cell magic") return line, cell # In an interactive session, we need to delete these to avoid # name conflicts for automagic to work on line magics. del lmagic, lcmagic
You can also create magics of all three kinds by inheriting from the
IPython.core.magic.Magics class. This lets you create magics that can
potentially hold state in between calls, and that have full access to the main
# This code can be put in any Python module, it does not require IPython # itself to be running already. It only creates the magics subclass but # doesn't instantiate it yet. from __future__ import print_function from IPython.core.magic import (Magics, magics_class, line_magic, cell_magic, line_cell_magic) # The class MUST call this class decorator at creation time @magics_class class MyMagics(Magics): @line_magic def lmagic(self, line): "my line magic" print("Full access to the main IPython object:", self.shell) print("Variables in the user namespace:", list(self.shell.user_ns.keys())) return line @cell_magic def cmagic(self, line, cell): "my cell magic" return line, cell @line_cell_magic def lcmagic(self, line, cell=None): "Magic that works both as %lcmagic and as %%lcmagic" if cell is None: print("Called as line magic") return line else: print("Called as cell magic") return line, cell # In order to actually use these magics, you must register them with a # running IPython. This code must be placed in a file that is loaded once # IPython is up and running: ip = get_ipython() # You can register the class itself without instantiating it. IPython will # call the default constructor on it. ip.register_magics(MyMagics)
If you want to create a class with a different constructor that holds additional state, then you should always call the parent constructor and instantiate the class yourself before registration:
@magics_class class StatefulMagics(Magics): "Magics that hold additional state" def __init__(self, shell, data): # You must call the parent constructor super(StatefulMagics, self).__init__(shell) self.data = data # etc... # This class must then be registered with a manually created instance, # since its constructor has different arguments from the default: ip = get_ipython() magics = StatefulMagics(ip, some_data) ip.register_magics(magics)
In early IPython versions 0.12 and before the line magics were
created using a
define_magic() API function. This API has been
replaced with the above in IPython 0.13 and then completely removed
in IPython 5. Maintainers of IPython extensions that still use the
define_magic() function are advised to adjust their code
for the current API.