7.2 Importing names

Python's module system is a powerful feature that allows you to organize and reuse code efficiently. By importing specific functions or entire modules, you can access a wide range of pre-built functionality to enhance your programs.

Understanding how to import modules and manage packages is crucial for writing clean, efficient Python code. This knowledge enables you to leverage the vast ecosystem of Python libraries, both built-in and third-party, to solve complex problems with ease.

Importing Modules and Functions in Python

Importing specific functions

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• Use

  [from](https://www.fiveableKeyTerm:From)

  keyword followed by module name and

  import

  to import specific functions from a module
  • Syntax:

    from module_name import function_name

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

    imports only

    sqrt

    function from

    math

    module
• Allows using imported function directly without prefixing it with module name
  • After importing

    sqrt

    from

    math

    , use as

    sqrt(4)

    instead of

    math.sqrt(4)

• Import multiple functions from a module by separating them with commas

  • from math import sqrt, [sin](https://www.fiveableKeyTerm:sin), [cos](https://www.fiveableKeyTerm:cos)

    imports

    sqrt

    ,

    sin

    , and

    cos

    functions from

    math

    module

Prevention of name collisions

• Name collisions occur when imported names conflict with existing names in code or other imported modules
• Use

  as

  keyword to create an alias for imported module or function to avoid name collisions
  • Syntax:

    import module_name as alias

    or

    from module_name import function_name as alias

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

    creates alias

    plt

    for

    matplotlib.pyplot

    module
• Using aliases prevents name collisions and makes code more readable by providing shorter or more descriptive name
• Another way to prevent name collisions is to import entire module and use module name as prefix when accessing its functions or variables

  • import math

    and then use

    math.sqrt(4)

    to avoid conflicts with other

    sqrt

    functions

Specific vs entire module imports

• Importing specific functions:
  • Advantages:
    • Use imported functions directly without prefixing with module name, making code more concise
    • Reduces risk of name collisions by only importing required functions
    • Can make code more readable by explicitly showing which functions are used from a module
  • Disadvantages:
    • Requires knowing exact names of functions to import
    • May result in longer import statements if importing many functions from a module
• Importing entire modules:
  • Advantages:
    • Access all functions and variables from module using module name as prefix
    • Requires less knowledge of specific function names within module
    • Can make import statement shorter if using many functions or variables from module
  • Disadvantages:
    • Increases risk of name collisions if module contains names that conflict with code or other imported modules
    • May make code less readable if module name is long or not descriptive enough
    • Can potentially import unnecessary functions or variables not used in code

Package Management and Libraries

• Python's standard library provides built-in modules for common tasks
• Third-party libraries extend Python's functionality beyond the standard library
• Use pip (Python package installer) to install and manage third-party libraries
• Packages are collections of modules organized in directories
  • The init.py file in a directory indicates it should be treated as a package
• Relative imports allow importing modules within the same package using dot notation