Modules
Single Py Files Containing |
Python components you have defined (functions, variables, classes, etc.) Runnable code (scripts) |
Can be: |
Executed (python my_module.py) Imported from a shell or another file |
IMPORTING |
When you import a module, a new name, 'bound' to the module, is created in the current scope: |
import math
x = math.pow(2, 3) |
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from math import pow
x = pow(2, 3) |
We can also import a specific function from the module, and so now we don't need to specify the module name |
from math import *
x = pow(2, 3) |
We could also achieve this by importing all objects in the module, but isk creating namespace conflicts: |
from math import *
x = pow(2, 3) |
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We can import a module under an alias to bind it to a name of our choice: |
import pandas as pd import seaborn as sns |
All runnable code in a module is executed at import. |
f you want it to be executed only when you run the file, use the following: |
if __name__ == "__main__":
print("This will be run only if the file is execut ed") |
__name__ is a special built-in variable which will automatically be set to "__main__" if the source file is being executed as the main program, rather than being imported. |
When importing, Python looks for the module with the same name in: |
The built-in modules |
The directories defined in the sys.path list: |
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The current working directory
The PYTHONPATH list
The default Python directory |
You can access this list at runtime and append new paths to it manually: |
import sys print(sys.path) sys.path.append("/path/to/add") |
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Code to treat Jupyter notebooks as modules
import io, os, sys, types
import nbformat
from IPython import get_ipython
from IPython.core.interactiveshell import InteractiveShell
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
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
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]
sys.meta_path.append(NotebookFinder()) |
Importing ipynb as modules
from NameOfModule import NameOfFunction |
from math import pow2 |
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Packages
Packages are directories that contain modules and/or other packages. This can be a good way to group modules in a hierarchical directory structure. |
__init__.py in a package will be executed at import. |
Can be used to import nested modules at a higher level of hierarchy |
When working with packages, it is recommended to assume code will be run from the top level and use absolute imports from there |
Add an extra level of hierarchy and a setup.py file |
To install run: pip install my_package/ (the / is important) |
Once installed, you can import your module from Python, or run an executable in the shell if you've defined an entrypoint. |
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