Python – Modules and Packages

• Any file containing logically organized Python code can be used as a module.

• A module generally contains any of the defined functions, classes and variables. A module can also include executable code.

• Any Python source file can be used as a module by using an import statement in some other Python source file.

Importing a module

Two ways of importing a module:

• First way:
  • Specify a module along with ‘import’ key word.
  • A dot operator can be used to access attributes and methods of imported module.

#mymath module
def square(x):
    'Returns square of a number'
    return x**2
#main.py
import mymath
n=[1,2,3,4,5]
s=[mymath.square(num) for num in n]
print(s)
#Output: [1, 4, 9, 16, 25]

• Second way:
  • Allows the user to directly access the attributes and methods of a module, without using a dot operator.
  • The attributes and methods of the imported module types are imported directly into the local namespace. And, they are available directly, without qualification by module name.
  • All the available attributes and methods, of a module can be imported using *.

#mymath module
def square(x):
    'Returns square of a number'
    return x**2
#main.py
from mymath import square
n=[1,2,3,4,5]
s=[square(num) for num in n]
print(s)
#Output: [1, 4, 9, 16, 25]

Packages

• A package is a collection of modules present in a folder.
• The name of the package is the name of the folder itself.
• A package generally contains an empty file named __init__.py in the same folder, which is required to treat the folder as a package.
• Python packages can contain other packages within them to an arbitrary depth — provided each sub-package also has its own ‘__init__.py’ file.