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Python notes - Day11 - package and file operations

2022-05-15 06:03:29Wandering mage 12

python Grammar learning , Leave it to those who need it , Understand everything !!

# coding=utf8
# @time:2022/4/20 15:04
# Author  Haoyu 

#  One 、 The operation of the package 
# 1. What is a bag 
#  The package is equivalent to a folder ( The module is equivalent to a file ), Packages are used to manage modules ;
 Bag is python It is specially used to manage py File folder , There is a special file in this folder ”
( The normal folder in the project is generally used to manage the non code files needed in the project , Such as : Audio 、 Video etc. )

# 2. How to use the contents of the package  -  Import 
1)import  package     -    After importing, you can use ‘ Package name .’ Use the... In this package .py All global variables defined in the file 
2)import  Package name . Module name  -    After importing, you can use ‘ Package name . Module name .’ To use all global variables in the specified module 
3)import  Modules in the package  as  New name   -   Directly rename the modules in the imported package 
4)from  Package name  import  Module name     -    Import the specified module in the specified package , After importing, you can use ‘ Module name .’ To use all the global variables in the module 
5)from  Package name . Module name  import  Variable 1, Variable 2,....   -    Import the specified variables in the specified module , Variables are used directly when they are used 
# 1) Direct import package 
# import filemannger
# print(filemannger.x)

# 2) Directly import the modules in the package 
# import filemannger.source
# filemannger.source.read_file() #  Reading documents 

# 3) Directly rename the modules in the imported package 
#  Be careful : If you call every time filemannger.source It will be very trouble , Here can be combined with renaming , If it is renamed as f1, After Mina can directly use f1
# import filemannger.source as f1
# f1.read_file() #  Reading documents 

# 4) Import modules directly through packages 
# from filemannger import source
# source.read_file() #  Reading documents 
# source.read_file() #  Reading documents 

# 5) Directly import the variables in the module in the package 
# from filemannger.source import x
# print(x) # 100

# 3.__init__ file 
# 1) When importing a package, specify the default imported module or variables in the module 
# from filemannger.source import x
# 2) Define some general functions 
# def common():
# print(' The generic function ')

#  Two 、 File operations 
#  File operations  ->  Operation file content 
# 1. Data persistence 
#  The data used and generated in the program are saved in the running memory by default , When the program ends, the data saved in the running memory will be automatically destroyed .
#  If you want the data not to be destroyed after the program ends , Store data on the hard disk .
#  Save the data to the hard disk , Data persistence .( Be careful : Data cannot be put directly into the hard disk , Must be saved by file )
#  Common file types when programming :txt、json、plist、 database ( The most commonly used )

# 2. File operations 
1) Basic steps : Open file -> Operation file ( Read operations 、 Write operations )-> Close file 
2) Open file ( The underlying layer is called c Language )
a. The path of the file to be opened 
 Absolute path : The full path of the file in the computer 
 Relative paths : use  .  Represents the current directory ( The current directory refers to the directory of the file where the code of the open file is currently written )
         use  ..  Represents the upper directory of the current directory  
b.mode  -    File open mode ( Determines whether the supported operation is read or write after the file is opened ; Determines whether the data object of the operation is a data string or binary )
 The value that determines how to open :r、w、a
r   -    read-only 
w   -    Just write : After opening, it will delete and empty the contents of the original file 
a   -    Just write : Add content after the original document 

 Determine the data type of the operation :t( The default value is )、b
t   -    The contents read and written to the file are of string type 
b   -    What you read and what you write into the file are bytes( Binary system ) type 

 Be careful : When opening a file mode You must choose one of these two sets of values , If the value of the second group is not selected , Indicates the selected by default t

# f=open('./sources/aaa.txt','at')
# #
# f.write('lixingyu')

# f=open('./sources/aaa.txt','ab')
# #
# f.write(bytes('123456',encoding='utf-8'))

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