1.4.5. Modules

Simply put, a file containing a Python script is called a module. It allow us to separate a code base into multiple files.
We can import a module to get access to its functions and variables.

%%file fibonacci.py
# Fibonacci numbers module

def fib_print(n):    # write Fibonacci series up to n
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()

def fib(n):   # return Fibonacci series up to n
    result = []
    a, b = 0, 1
    while a < n:
        result.append(a)
        a, b = b, a+b
    return result

Overwriting fibonacci.py

import fibonacci


fibonacci.fib_print(10)
fibonacci.fib(10)

0 1 1 2 3 5 8 

[0, 1, 1, 2, 3, 5, 8]

1.4.5.1. More on Modules

It is possible to directly import a function or variable from a module.

from fibonacci import (
    fib_print,
    fib,
)


fibonacci.fib_print(10)
fibonacci.fib(10)

0 1 1 2 3 5 8 

[0, 1, 1, 2, 3, 5, 8]

During import, the as allows to bound a module to a different name in the local namespace.

import fibonacci as fib


fib.fib(10)

[0, 1, 1, 2, 3, 5, 8]

Both variations shown above can be used together.

from fibonacci import fib as fibonacci

fibonacci(10)

[0, 1, 1, 2, 3, 5, 8]

1.4.5.2. Executing modules as scripts

Running a Python module with

python [filename] <arguments>

executes the code in the module, similarly to importing it, but sets the __name__ to "__main__".
Therefore, we can modify the module to allow some code execution when called as a script using:

if __name__ == "__main__":
    pass

%%file fibonacci.py
# Fibonacci numbers module

def fib_print(n):    # write Fibonacci series up to n
    a, b = 0, 1
    while a < n:
        print(a, end=' ')
        a, b = b, a+b
    print()

def fib(n):   # return Fibonacci series up to n
    result = []
    a, b = 0, 1
    while a < n:
        result.append(a)
        a, b = b, a+b
    return result

if __name__ == "__main__":
    import sys
    fib_print(int(sys.argv[1]))

Overwriting fibonacci.py

Executing the module as a script will now run the fib_print function with the given argument.

! python fibonacci.py 10

0 1 1 2 3 5 8 

However, importing the module will not execute the fib_print function.

import fibonacci

1.4.5.3. Packages

Python packages are a dotted notation to structure module within directories.
For example, a module ./A/B.py would be imported with import A.B.

# Importing the `path` module, from the std lib `os`.
import os.path