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package use
A module is a py file. In order to classify and manage modules in Python, different folders need to be divided. Multiple related modules can be placed in the same folder. For the convenience of calling, a code folder in Python is generally called a package.
1. How to import packages
The following package newmsg is available. There are two modules in the package, namely sendmsg.py and recvmsg.py files. In the parent folder of the package, there is a test.py file, the goal is to introduce two modules of newmsg in the test.py file.
The directory structure is shown in the figure below:
- newmsg/
- __init__.py
- sendmsg.py
- recvmsg.py
- test.py
The contents of the sendmsg.py file are as follows:
def send_msg():
print('------sendmsg方法被调用了-------')
The contents of the recvmsg.py file are as follows:
def recv_msg():
print('-----recvmsg方法被调用了--------')
There are several ways to import a module and use the methods in the module.
- Import the specified module directly using packagename.modulemodulename.
import newmsg.sendmsg
- Use from xxx import xxx to import the specified module.
from newmsg import sendmsg
- Use the __init__.py file to import the specified modules in the package.
You can create an __init__.py file in newmsg, and import the specified content in this file.
Write the code in the __init__.py file:
from . import sendmsg # 导入指定的模块 . 代表的是当前文件夹
The code in the test.py file:
import newmsg
newmsg.sendmsg.send_msg() # 可以直接调用对应的方法
# newmsg.recvmsg.recv_msg() 不可以使用 recvmsg 模块，因为 __init__.py文件里没有导入这个模块
- Use the __init__.py file, combined with the __all__ attribute, to import all modules in the package.
Write code in the __init__.py file in the newmsg package:
__all__ = ["sendmsg","recvmsg"] # 指定导入的内容
test.py file code:
from newmsg import * # 将newmsg里的__inint__.py文件里,__all__属性对应的所有模块都导入
sendmsg.send_msg()
recvmsg.recv_msg()
Summarize
The package organizes related modules together, that is, puts them in the same folder, and creates a file named __init__.py in this folder, then this folder is called a package, which effectively avoids the problem of module name conflicts , making the application organization structure clearer.
2. What is the use of the init.py file
init.py controls the import behavior of the package. The init.py is empty only to import this package, and will not import the modules in the package. Content can be written in the __init__.py file.
newmsg/ init.py file:
print('hello world')
When other modules import this package, they will automatically call this code.
3. all
In the __init__.py file, define a __all__ variable that controls the modules imported when from package name import *.
newmsg/ init.py file:
__all__ = ['sendmsg','recvmsg']
Precautions
When customizing modules, you need to pay attention to the fact that the custom module name should not be the same as the system module name, otherwise problems will occur!
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