Python——Introducing the import method into the module

This article mainly introduces relevant information that explains in detail the examples of modules introduced by the Python import method. In Python, use import or from...import or from...import...as... to import the corresponding module. Friends who need it can refer to it

Detailed explanation of examples of modules introduced by the Python import method

In Python, use import or from...import or from...import...as... to import the corresponding module. The functions and usage methods are the same as The include header file in C language is similar. In fact, it is to introduce some mature function libraries and mature methods to avoid reinventing the wheel and improve development speed.

Python's import method can introduce system modules, or we can introduce shared modules written by ourselves. This is very similar to PHP, but their specific details are not quite the same. Because php specifies the specific path of the imported file when importing, and python cannot write the file path for importing.

The following is a summary of several situations of import:

Python’s method of including modules in subdirectories is relatively simple. The key is to be able to find the path to the module in sys.path The path to the file.

The following will introduce several common situations in detail:

(1) The main program and the module program are in the same directory:

The program structure is as follows :

-- src 
|-- mod1.py 
– test1.py

If you import the module mod1 in the program test1.py, directly use import mod1 or from mod1 import *;

(2 ) The directory where the main program is located is the parent (or ancestor) directory of the directory where the module is located

The program structure is as follows:

-- src 
|-- mod1.py 
|-- mod2 
|– mod2.py 
`– test1.py

If To import the module mod2 in the program test1.py, you need to create an empty file init.py file in the mod2 folder (you can also customize the output module interface in this file); then use from mod2.mod2 import * or import mod2.mod2 .

(3) The main program imports modules in the upper directory or modules under other directories (horizontal)

The program structure is as follows:

-- src 
|-- mod1.py 
|-- mod2 
|– mod2.py 
|– sub 
| -- test2.py 
– test1.py

If you import the modules mod1 and mod2 in the program test2.py. First, you need to create the init.py file under mod2 (same as (2)). There is no need to create this file under src. Then the calling method is as follows:

The following program execution methods are all executed in the directory where the program file is located. For example, test2.py is executed after cd sub; python test2.py

And test1.py is executed after cd src; python test1.py; is not guaranteed to be successful in executing python sub/test2.py in the src directory.

import sys 
sys.path.append(“..”) 
import mod1 
import mod2.mod2

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