callipy 0.3

Calling IPython notebooks with arguments

Dependencies

• runipy: https://github.com/paulgb/runipy

• IPython (tested with IPython 2.3.0)

Installation

pip install callipy

Simple Usage

Let’s create a notebook called notebook.ipynb, containing the following cell:

y = 2 * x

Now let’s call this notebook from another session with a value for x and get the result y:

>>> import callipy
>>> callipy.call_notebook("notebook.ipynb", x=2).y
4

How it works

First the keyword arguments given to call_notebook are injected into the notebook’s namespace and runipy is used to execute all of its cells:

>>> result = callipy.call_notebook("notebook.ipynb", x=2)
>>> result
<callipy.NotebookResult at 0x106b92f10>

After running the notebook, the value of any variable in the notebook’s namespace can be read using attribute or dict notation:

>>> result.y
4
>>> result['y']
4

Note: arguments and output values must be pickleable.

Finally, the notebook object itself can be accessed as result.notebook. See https://github.com/paulgb/runipy for examples of things you can do with the notebook object.

Default values and validation

That’s all good and well, but we have a slight problem: if we try to run the target notebook on its own, it will complain about x not being defined.

The solution is to declare the parameters and their default value at the beginning of notebook.ipynb:

%load_ext callipy
%param x 5

Now we can run the notebook from the browser, or call it without arguments, and it will use the default value for every missing argument:

>>> callipy.call_notebook("notebook.ipynb").y
10

When more than one value is given, the parameter behaves as an enumerated type and the first value is the default value:

%param mode "simple", "advanced"

If the notebook is called with a value that was not declared, an error will be raised:

>>> callipy.call_notebook("notebook.ipynb", mode="wrong")
ValueError: Invalid value 'wrong' for parameter mode: "simple", "advanced"

You can customise this behaviour by giving as the default value an object mydefault that supports the following:

• mydefault[0]: returns the default value

• x in mydefault: tests whether x is allowed

Note that a lone string is treated as an atomic value, not as an enumeration of characters:

%param a "test" # the default value is 'test'
%param b list("test") # the default value is 't'

Finally, a notebook can be queried for the parameters it declares:

>>> callipy.get_notebook_params("notebook.ipynb")
{'x': 5, 'mode': ("simple", "advanced")}

Caveat: to extract this information, callipy must execute the notebook. What if this takes time or produces side-effects? To alleviate the problem, the instruction %params_done can be placed in the notebook:

%param x 5
%param mode "simple", "advanced"
%params_done

Then when calling get_notebook_params() anything after this cell will be ignored.

Acknowledgments

Based on the good work by @paulgb: https://github.com/paulgb/runipy

Any reference to a famous statue is purely coincidental.