8. What is a module? module import __name __, module _ name _

8. What is a module? module import __name __, module _ name _
What is a module:

In Python, modules are the repositories of methods and classes. If we want to use a method or class, we need to import the corresponding template.

[Python has built-in methods and classes, so we do not need to import modules for some methods]

 

Module usage: module. function, module. Class

Module import:

 

• Module import:
  • Import Module name

  # Import module name import mathprint (math. sqrt (9 ))

• From... Import Statement: import a specified part from the module, such as a class or method, where from... Import * Indicates importing all content

# From Module name import class name, method name from collections import Iterable print (isinstance ("abc", Iterable) print (isinstance ([1, 2, 3], Iterable ))

• From... During import, you can also give the imported part a custom name, for example, from... Import funcA as fa

 

• Import from the module:

Search Path of Python import
1. Search for this module in the current directory
2. Search for the path list specified in the environment variable PYTHONPATH in sequence [available from sys. path]
Import sysprint (sys. path) ---------- running result: ['J: \ HardWork \ Code \ python', 'J: \ HardWork \ Code \ python', 'I: \ python3 \ python36.zip ',' I :\\ python3 \ DLLs ',' I: \ python3 \ lib ',' I :\\ python3 ', 'I: \ python3 \ lib \ site-packages']
3. Search for the lib library in the Python installation path 

 

 

Directory structure:

C content:

How to import c in B:

Import sys, osprint (_ file _) # This is the absolute path of the current file, parent_dir = OS. path. dirname (_ file _) # obtain the directory pp_dir = OS of the current file. path. dirname (parent_dir) sys. path. append (pp_dir) # print (sys. path) import c # To import c, you must add diff_dir to sys. path

 

 

_ Name __:

Since the module can be imported or run directly, to distinguish the content that runs when running directly, you have _ name __:

 

When running directly, __name _ is _ main __:

Print ("import C done") print (_ name _) if _ name __= = '_ main _': print ("direct run ") --------------- run result: import C done _ main _ direct run

When used for import, __name _ is the name of the currently imported module. Because _ name _ is not equal to _ main __, it is not executed:

Import sys, OS # print (_ file _) # This is the absolute path of the current file, parent_dir = OS. path. dirname (_ file _) # obtain the directory pp_dir = OS of the current file. path. dirname (parent_dir) sys. path. append (pp_dir) # print (sys. path) import c # To import c, you must add diff_dir to sys. in path ------------------ running result: import C donec