This is the 23rd day of my participation in Gwen Challenge

Modules and packages

In Python, a.py file is called a Module.

A package is a folder that contains modules with a special __init__.py file, which indicates to Python that the folder is special because it contains Python modules.

Note that the name of the built-in module is not the same as the name of the built-in module.

The code is as follows:

#! /usr/bin/env python3
# -*- coding: utf-8 -*-

' a test module '

__author__ = 'Michael Liao'

import sys

def test() :
    args = sys.argv
    if len(args)==1:
        print('Hello, world! ')
    elif len(args)==2:
        print('Hello, %s! ' % args[1])
    else:
        print('Too many arguments! ')

if __name__=='__main__':
    test()

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The py file itself uses standard UTF-8 encoding. Line 4 is a string representing the module’s documentation comment. The first string of any module code is treated as the module’s documentation comment. Line 6 uses the __author__ variable to include the author, so that when you publish the source code, others can see your name.

Installing third-party Modules

In general, third-party libraries are registered at the Official Python site, pypi.python.org

There are image processing library Pillow, Web framework Flask, Scientific computation Numpy, and so on

Installing Anaconda automatically installs dozens of third-party modules, making it easy to use

Module search path

By default, the Python interpreter searches the current directory, all installed built-in modules, and third-party modules in the sys module’s path variable:

import sys
print(sys.path)
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There are two ways to add your own search directory:

  1. Modify sys.path directly to add the directory to search for :(modified at run time, invalid after run)sys.path.append('/Users/michael/my_py_scripts')
  2. Setting environment VariablesPYTHONPATHThe contents of the environment variable are automatically added to the module search path. The setting is similar to setting the Path environment variable. Note that you only need to add your own search path. Python’s own search path is not affected.

scope

Classified as public and non-public (private) Generally begins with an underscore _ or a double underscore __

Private functions and variables “should not” be referred to directly, rather than “cannot”, because Python does not have a way to completely restrict access to private functions or variables. However, it is programming convention not to refer to private functions or variables.

Summary:

All external functions that do not need to be referenced are defined as private, and only external functions that need to be referenced are defined as public

This should belong to the object oriented idea, after encapsulating this module to provide the public function or variable for other use

The last

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