What is a module: py files are modules

What is a package: contains__ init__.py module folder (directory)

The function of modules and packages is to organize code

Note: the directory is not a package. There is no directory in it__ init__.py module

1, Module import

Use functions, variables and classes in other modules to import modules

Function: Use / call the written code

Module import method:

from path route. Module name # import # class name (function name)

import path route. The module name path starts from the project root directory

import package name

import ddt
import json
import unittest
from FutureLoan.common.requests_handler import visit
from FutureLoan.middleware.MiddleHandler import MidInitHandler

2, Module classification

Built in module: Python's own module, import os

Third library module: modules written by others need to be installed. pip install requests，import. . . . from····import······

Custom module: a module written by yourself, usually in a package. from package import module

Extended content:

from ... Import * ------ > means to import all code from the module

from FutureLoan.common.requests_handler import * 
# Don't use it generally. It may have the same name as the function in this module

from .....import sth as other indicates as renaming, alias

from FutureLoan.common.requests_handler import visit as visit_new

Print import module path

import sys
print(sys.path)

'''
['D:\\Program Files (x86)\\PyCharm\\workspace\\Lemon', 'D:\\Program Files (x86)\\PyCharm\\workspace', 'D:\\Program Files (x86)\\PyCharm\\workspace\\SmartCampus_web', 'D:\\Program Files (x86)\\Python38\\python38.zip', 'D:\\Program Files (x86)\\Python38\\DLLs', 'D:\\Program Files (x86)\\Python38\\lib', 'D:\\Program Files (x86)\\Python38', 'D:\\Program Files (x86)\\Python38\\lib\\site-packages', 'D:\\Program Files (x86)\\Python38\\lib\\site-packages\\win32', 'D:\\Program Files (x86)\\Python38\\lib\\site-packages\\win32\\lib', 'D:\\Program Files (x86)\\Python38\\lib\\site-packages\\Pythonwin']
'''

III__ name__

Represents the module name of the current file

Run files and scripts {1 Is a module, is a special module 2 We run the program through this file

Run in the form of module import__ name__ File name and module name

Directly running files, scripts__ name__ It is not a file name or module name, but a fixed one:__ main__

demo.py
if __name__=='__mian__':
    print('demo')

demo1.py
if __name__=='__mian__':
    print('demo1')

demo2.py
if __name__=='__mian__':
    print('demo2')

demo3.py
from LianXi.test1 import demo
from LianXi.test1 import demo1
from LianXi.test1 import demo2
if __name__=='__mian__':
    print('demo3')                   #The results after operation are: demo3

demo.py
if __name__=='__mian__':
    print('demo')

demo1.py
if __name__=='__mian__':
    print('demo1')

demo2.py
if __name__=='__mian__':
    print('demo2')

demo3.py
from LianXi.test1 import demo
from LianXi.test1 import demo1
from LianXi.test1 import demo2
print('demo3')                   #The results after operation are: demo demo1  demo2  demo3

Question 1: import module Is it OK to write the function like this?

For example: import Lianxi test1. demo. visit
It's not allowed to write like this

Import modules and find the order of modules: project directory – Python installation directory (lib) -- pip install third-party module (site package)
You can import built-in and third-party modules directly into sth without writing a path
When importing custom modules, you usually start from the bottom of the root directory, and you need to write the path
You can directly import the Python module into the site package directory instead of the custom module directory

4, os module

import os# mainly deals with system related operations

Mainly use OS Path to handle system path related operations

import os.path or from os import path

# Get the absolute path of the file (use the most, because the absolute path will not change)
print(os.path.abspath(__file__))
print(__file__)
print(__name__)

'''
D:\Program Files (x86)\PyCharm\workspace\Lemon\0714.py
D:/Program Files (x86)/PyCharm/workspace/Lemon/0714.py
__main__
'''

Absolute path: start from the system's drive letter or system root directory

Relative path: a way of saying that one path is relative to another

__ file__: The path of the current file may be absolute or relative

__ name__: Module name, no path

import os
# Get file absolute path
file_path = os.path.abspath(__file__)
print("file_path:",file_path)
# Get the upper level path
dir_name = os.path.dirname(file_path)
# Path splicing
print(os.path.join(dir_name,'demo.txt'))

'''
file_path: D:\Program Files (x86)\PyCharm\workspace\Lemon\0714.py
D:\Program Files (x86)\PyCharm\workspace\Lemon\demo.txt
'''

Note: all the obtained paths are only the representation of a path, and do not mean that the file or path really exists

# Get current working directory
print(os.getcwd())
# Create a new directory (folder)
print(os.mkdir('class_2'))
# Determine whether a path exists
print(os.path.exists(os.getcwd()))
# Determine whether the current path is a file
print(os.path.isfile(os.getcwd()))
# Determine whether the current path is a directory
print(os.path.isdir(os.getcwd()))

'''
D:\Program Files (x86)\PyCharm\workspace\Lemon
None
True
False
True
'''