What Is Module

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∟What Is Module

This section provides a quick introduction of module, which is an object of the 'module' data type that can store attributes, functions, classes and sub-modules.

What Is a Module? A module is an object of the "module" data type that can store attributes, functions, class classes.

Here are the guidelines you should remember on using modules.

1. There is no Python statement that defines a module.

2. A module is defined in an external file.

The file name follow this syntax: module_name.py.
Statements in the file are module sub-statements.

3. A module is imported into memory using the "import" statement, using these syntax:

import module_name
import module_name as variable_name

When an "import module_name" statement is executed, Python system will do the following:

Search for the module file, module_name.py, in locations given in sys.path.
Load the module file in memory.
Execute sub-statements stored in the module file. This may define variables (attributes), functions and classes in the module.
Create a "module" object to store module's attributes, functions and classes defined during the execution.
Declare a variable with the given variable_name or module_name.
Assign the "module" object to the variable.

Here is an example of a module file, module_test.py:

#  module_test.py
#- Copyright 2011 (c) HerongYang.com. All Rights Reserved.
#
print("Hi there! - from 'module_test' module")

version = "1.00 - from 'version' attribute"

def help():
   print("How can I help you? - from 'help()' function")

class first:
   print("Welcome on board! - from 'first' class")
   count = 0
   def rise(self):
      first.count += 1
      print(f"count = {first.count} - from 'rise()' method")

You can save module_test.py in the current directory and run the following code in Python shell to test it.

herong$ ls -l
-rw-r--r--@ 1 herong  staff  423 Apr 1 07:35 module_test.py

herong$ python

# import the module
>>> import module_test
Hi there! - from 'module_test' module
Welcome on board! - from 'first' class

# check the module object
>>> m = module_test
>>> type(m)
<class 'module'>
>>> id(m)
4309263360

# check module attribute 'version' and function 'help()'
>>> m.version
"1.00 - from 'version' attribute"
>>> m.help()
How can I help you? - from 'help()' function

# create an instance from the module class 'first'
>>> f = m.first()
>>> f.rise()
count = 1 - from 'rise()' method
>>> f.rise()
count = 2 - from 'rise()' method