Detailed explanation of file operations in python3

Steps: Open the file-"Operate the file-"Close the file

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Open the file

文件句柄 = open('文件路径', '模式')

Specify the file encoding

文件句柄= open('文件路径','模式',encoding='utf-8')

In order to prevent forgetting to close the file, you can use the context manager to open the file

with open('文件路径','模式') as 文件句柄:

The modes for opening files are:

• r, read-only mode (default).

• w, write-only mode. [Unreadable; create if it does not exist; delete the content if it exists;]

• a, append mode. [Readable; if it does not exist, create it; if it exists, only append the content;]

• r+, the file can be read and written. [Readable; Writable; Appendable]

• w+, write and read

"U" means that when reading, you can r \n \r\n is automatically converted to \n (same as r or r+ mode)

• rU

• r+U

"b" means processing binary files (such as: FTP sending and uploading ISO image files, Linux can be ignored, Windows needs to be marked when processing binary files)

• rb

• ##wb

• ab

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Close file

文件句柄.close()

Operation file:

detach

#占位

fileno (returns file descriptor, used for I/O operations of the underlying operating system)

fid = 文件句柄.fileno()print(fid)

flush (refresh the buffer and write the data in the buffer to the file immediately)

文件句柄.flush()

isatty (determine whether the file is connected to a terminal device and return a Boolean value)

文件句柄.isatty()

read (read the specified number of characters from the file, read all by default)

str = 文件句柄.read()      #读取整个文件
str1 = 文件句柄.read(10)   #读取文件前10个字符

readable (determine whether the file is readable, return a Boolean value)

文件句柄.readable()

readline (each time Read at most one line of data, and the end of each line contains the newline character '\n')

print(文件句柄.readline())   #读取第一行数据print(文件句柄.readline(3))  #读取第二行前3个字符print(文件句柄.readline())   
#读取第二行剩余字符print(文件句柄.readline())   #读取第三行

seek (Move the pointer for file reading. If the file contains Chinese, the moving pointer must be a multiple of 3, otherwise it will An error is reported because one Chinese character is equal to 3 bytes)

文件句柄.seek(6)

seekable (determines whether the file pointer is available and returns a Boolean value)

文件句柄.seekable()

tell (gets the pointer position)

文件句柄.tell()

truncate (truncate, delete the content behind the pointer, and write it to the file, operate in writable mode)

f = open('text.txt','r+',encoding='utf-8')
f.seek(9)   #把指针移动到第9个字节后面（即第3个中文后面）f.truncate()  #把第3个中文后面的字符删除，并写入文件f.close()

writable (determine whether the file is writable, return a Boolean value)

文件句柄.writable()

write (write the string to the file and return the number of characters)

文件句柄.write('字符串')

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