Importing IPython Notebooks as Modules¶
It is a common problem that people want to import code from IPython Notebooks. This is made difficult by the fact that Notebooks are not plain Python files, and thus cannot be imported by the regular Python machinery.
Fortunately, Python provides some fairly sophisticated hooks into the import machinery, so we can actually make IPython notebooks importable without much difficulty, and only using public APIs.
import io, os, sys, types
import nbformat
from IPython import get_ipython
from IPython.core.interactiveshell import InteractiveShell
Import hooks typically take the form of two objects:
- a Module Loader, which takes a module name (e.g.
'IPython.display'), and returns a Module - a Module Finder, which figures out whether a module might exist, and tells Python what Loader to use
def find_notebook(fullname, path=None):
"""find a notebook, given its fully qualified name and an optional path
This turns "foo.bar" into "foo/bar.ipynb"
and tries turning "Foo_Bar" into "Foo Bar" if Foo_Bar
does not exist.
"""
name = fullname.rsplit('.', 1)[-1]
if not path:
path = ['']
for d in path:
nb_path = os.path.join(d, name + ".ipynb")
if os.path.isfile(nb_path):
return nb_path
# let import Notebook_Name find "Notebook Name.ipynb"
nb_path = nb_path.replace("_", " ")
if os.path.isfile(nb_path):
return nb_path
Notebook Loader¶
Here we have our Notebook Loader. It's actually quite simple - once we figure out the filename of the module, all it does is:
- load the notebook document into memory
- create an empty Module
- execute every cell in the Module namespace
Since IPython cells can have extended syntax, the IPython transform is applied to turn each of these cells into their pure-Python counterparts before executing them. If all of your notebook cells are pure-Python, this step is unnecessary.
class NotebookLoader(object):
"""Module Loader for IPython Notebooks"""
def __init__(self, path=None):
self.shell = InteractiveShell.instance()
self.path = path
def load_module(self, fullname):
"""import a notebook as a module"""
path = find_notebook(fullname, self.path)
print ("importing notebook from %s" % path)
# load the notebook object
nb = nbformat.read(path, as_version=4)
# create the module and add it to sys.modules
# if name in sys.modules:
# return sys.modules[name]
mod = types.ModuleType(fullname)
mod.__file__ = path
mod.__loader__ = self
mod.__dict__['get_ipython'] = get_ipython
sys.modules[fullname] = mod
# extra work to ensure that magics that would affect the user_ns
# actually affect the notebook module's ns
save_user_ns = self.shell.user_ns
self.shell.user_ns = mod.__dict__
try:
for cell in nb.cells:
if cell.cell_type == 'code':
# transform the input to executable Python
code = self.shell.input_transformer_manager.transform_cell(cell.source)
# run the code in themodule
exec(code, mod.__dict__)
finally:
self.shell.user_ns = save_user_ns
return mod
The Module Finder¶
The finder is a simple object that tells you whether a name can be imported, and returns the appropriate loader. All this one does is check, when you do:
import mynotebook
it checks whether mynotebook.ipynb exists.
If a notebook is found, then it returns a NotebookLoader.
Any extra logic is just for resolving paths within packages.
class NotebookFinder(object):
"""Module finder that locates IPython Notebooks"""
def __init__(self):
self.loaders = {}
def find_module(self, fullname, path=None):
nb_path = find_notebook(fullname, path)
if not nb_path:
return
key = path
if path:
# lists aren't hashable
key = os.path.sep.join(path)
if key not in self.loaders:
self.loaders[key] = NotebookLoader(path)
return self.loaders[key]
Register the hook¶
Now we register the NotebookFinder with sys.meta_path
sys.meta_path.append(NotebookFinder())
After this point, my notebooks should be importable.
Let's look at what we have in the CWD:
ls nbpackage
So I should be able to import nbimp.mynotebook.
Aside: displaying notebooks¶
Here is some simple code to display the contents of a notebook with syntax highlighting, etc.
from pygments import highlight
from pygments.lexers import PythonLexer
from pygments.formatters import HtmlFormatter
from IPython.display import display, HTML
formatter = HtmlFormatter()
lexer = PythonLexer()
# publish the CSS for pygments highlighting
display(HTML("""
<style type='text/css'>
%s
</style>
""" % formatter.get_style_defs()
))
def show_notebook(fname):
"""display a short summary of the cells of a notebook"""
nb = nbformat.read(fname, as_version=4)
html = []
for cell in nb.cells:
html.append("<h4>%s cell</h4>" % cell.cell_type)
if cell.cell_type == 'code':
html.append(highlight(cell.source, lexer, formatter))
else:
html.append("<pre>%s</pre>" % cell.source)
display(HTML('\n'.join(html)))
show_notebook(os.path.join("nbpackage", "mynotebook.ipynb"))
So my notebook has a heading cell and some code cells, one of which contains some IPython syntax.
Let's see what happens when we import it
from nbpackage import mynotebook
Hooray, it imported! Does it work?
mynotebook.foo()
Hooray again!
Even the function that contains IPython syntax works:
mynotebook.has_ip_syntax()
Notebooks in packages¶
We also have a notebook inside the nb package,
so let's make sure that works as well.
ls nbpackage/nbs
Note that the __init__.py is necessary for nb to be considered a package,
just like usual.
show_notebook(os.path.join("nbpackage", "nbs", "other.ipynb"))
from nbpackage.nbs import other
other.bar(5)
So now we have importable notebooks, from both the local directory and inside packages.
I can even put a notebook inside IPython, to further demonstrate that this is working properly:
import shutil
from IPython.paths import get_ipython_package_dir
utils = os.path.join(get_ipython_package_dir(), 'utils')
shutil.copy(os.path.join("nbpackage", "mynotebook.ipynb"),
os.path.join(utils, "inside_ipython.ipynb")
)
and import the notebook from IPython.utils
from IPython.utils import inside_ipython
inside_ipython.whatsmyname()
This approach can even import functions and classes that are defined in a notebook using the %%cython magic.