11.5 Using modules with classes

Python's module system allows you to import and use classes from other files, promoting code organization and reusability. By importing specific classes or using aliases, you can streamline your code and make it more readable.

Modules help group related classes together, making your codebase more manageable. This approach supports object-oriented programming concepts like inheritance and encapsulation, while also enabling the creation of larger, more complex packages.

Importing and Using Classes from Modules

Importing specific classes

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• Use

  from

  keyword followed by module name and

  import

  keyword to import specific classes from a module
  • Syntax:

    from module_name import ClassName1, ClassName2

  • Allows using imported classes directly without prefixing them with module name
• Example:

  from [math](https://www.fiveableKeyTerm:Math) import [sqrt](https://www.fiveableKeyTerm:sqrt), [pi](https://www.fiveableKeyTerm:pi)

  • Imports

    sqrt

    function and

    pi

    constant from

    math

    module
  • Can use

    sqrt(x)

    and

    pi

    directly in code without prefixing with

    math.

• Example:

  from [datetime](https://www.fiveableKeyTerm:datetime) import [date](https://www.fiveableKeyTerm:date), [time](https://www.fiveableKeyTerm:Time)

  • Imports

    date

    and

    time

    classes from

    datetime

    module
  • Can create instances of

    date

    and

    time

    classes directly, e.g.,

    today = date.today()

Aliases for module renaming

• Use

  [as](https://www.fiveableKeyTerm:as)

  keyword to give an alias to an imported module or class
  • Syntax:

    import module_name as alias

    or

    from module_name import ClassName as alias

• Renaming modules or classes with aliases improves code readability and avoids naming conflicts
  • Example:

    import [numpy](https://www.fiveableKeyTerm:NumPy) as np

    • Imports

      numpy

      module and assigns it alias

      np

    • Can use

      np

      instead of

      numpy

      to refer to the module, e.g.,

      np.array([1, 2, 3])

  • Example:

    from [matplotlib](https://www.fiveableKeyTerm:Matplotlib) import [pyplot](https://www.fiveableKeyTerm:pyplot) as plt

    • Imports

      pyplot

      module from

      matplotlib

      and assigns it alias

      plt

    • Can use

      plt

      instead of

      pyplot

      to refer to the module, e.g.,

      plt.plot(x, y)

• Aliases help manage namespaces by providing shorter, more convenient names for modules or classes

Modules for code organization

• Group related classes into a single module file to improve code organization and maintainability
  • Example: Create module file named

    shapes.py

    containing related classes like

    [Circle](https://www.fiveableKeyTerm:Circle)

    ,

    [Rectangle](https://www.fiveableKeyTerm:Rectangle)

    , and

    [Triangle](https://www.fiveableKeyTerm:Triangle)

• Importing classes from a module allows reusing them in different parts of your program or in other programs
  • Example: In main program file, import classes from

    shapes

    module:

    from shapes import Circle, Rectangle, Triangle
    

  • Allows creating instances of

    Circle

    ,

    Rectangle

    , and

    Triangle

    classes in main program
• Organizing classes into modules promotes code reusability and modularity
  • Can share module file containing classes with other developers or use it in different projects
  • Modular code is easier to understand, test, and maintain
• Example: Create module file named

  utils.py

  containing utility classes like

  [FileHandler](https://www.fiveableKeyTerm:FileHandler)

  ,

  [DatabaseConnector](https://www.fiveableKeyTerm:DatabaseConnector)

  , and

  [Logger](https://www.fiveableKeyTerm:Logger)

  • Can import and use these classes in different parts of the program or in other projects
  • Keeps main program file focused on core functionality while separating utility classes into a separate module

Object-Oriented Programming Concepts

• Inheritance: Allows a class to inherit attributes and methods from another class
• Encapsulation: Bundling of data and methods that operate on that data within a single unit (class)
• Polymorphism: Ability of objects of different classes to respond to the same method call
• Abstraction: Simplifying complex systems by modeling classes based on essential properties and behaviors
• These concepts are fundamental to object-oriented programming and can be implemented using modules and classes

Packages

• Collections of related modules grouped together in a directory
• Used to organize larger codebases and avoid naming conflicts
• Can contain sub-packages for further organization
• Imported using dot notation, e.g.,

  import package.subpackage.module