Operation of files for basic introduction to python

**python** file operation 
1. Open the file 
    Open the file: open(file, mode='r') 
        file: the path of the operation file plus the file name 
        #absolute path: starting from the root directory 
        #relative path: from a certain The path starts 
        mode: the mode (permission) of the file to                 open 
            the file permission: 
                r(read): read 
                w(write): write 
                a(apped): append 
Read, or write 
                r+: read and write, do not create a new file, the file read and write pointer is at the beginning 
                w+: read and write, create a new file, the read and write pointer is at the beginning, if the file exists, overwrite the original content of the file 
                a+: read and write, Create a new file, the read and write pointer is at the end, and the previous file will not be overwritten. 
                With write permission, when a non-existing file is opened, the file is created 
2. Read and write file 
    * read file * 
        str = read([num]) When reading a file, you can specify the number of bytes to read or do not specify 
        **read-write pointer**: 
            when the file is read and written, the disk will temporarily put the file in the memory, and the pointer will be shared when reading and writing the file.
            The file.seek(offset[,whence]) function can modify the file position pointer 
                offset: offset 
                whence: offset position, 0 from the beginning of the file, 1 from the current position, 2, from the end of the file 
                ***Note** *If the file is opened in a or a+ mode, the file operation flag will automatically 
                return to the end of the file every time a write operation is performed 
                *** Move the pointer to the beginning of the file Function: file.seek(0,0) 
        str = readLine() Read a line of strings 
        list = readLines(num) Read multiple lines and return to a list 
    **Write a file** 
        write('str'): Write a string in a file 
            This method does not join at the end of the string '\n' newline symbol, and when writing, it will prompt the number of bytes written 
        file.flush(): flush the content in the buffer to the disk, you can also use file.close() to flush Buffer 
        file.writelines(list_of_string): write a list of strings to a file