IO stream ----- open

io flow
         It mainly refers to the operation of computer input and output , Generally speaking, it is the input and output between memory and disk
        IO Stream operation is a kind of persistence operation , Is to persist data on disk
python How to operate io flow
            adopt open Global function ----- The main function is to open local files
         open Function analysis ：
     The first parameter ：file   The file name or path of the open file
     The second parameter ：mode   Turn on mode （ Default character input stream ）
     The other parameters

mode:
     'r'       open for reading (default)
    'w'       open for writing, truncating the file first
    'x'       create a new file and open it for writing
    'a'       open for writing, appending to the end of the file if it exists
    'b'       binary mode
    't'       text mode (default)
    '+'       open a disk file for updating (reading and writing)
    'U'       universal newline mode (deprecated)
Operation example ：

     from os import path          # Import io flow 
    >>> path.abspath(".")
    'C:\\Users\\hp'                     # View current path 
    >>> open("fg.txt")               # Open the file in the current path 
    <_io.TextIOWrapper name='fg.txt' mode='r' encoding='cp936'>
    >>> f=open("fg.txt","r")
    >>> path.abspath(".")
    'C:\\Users\\hp'
    >>> open("fg.txt")
    <_io.TextIOWrapper name='fg.txt' mode='r' encoding='cp936'>
    >>> open("C:\\Users\\hp\\fg.txt")
    <_io.TextIOWrapper name='C:\\Users\\hp\\fg.txt' mode='r' encoding='cp936'>
    >>> f.read()
    ''
    >>> f.close()

IO Stream classification ：
     According to the flow of data （ From the perspective of memory ） The direction of
   1、 Input stream
   /2、 Output stream
problem ： Is it an input stream or an output stream to save data in the hard disk ？------- Output stream
    3、 Byte stream ： Store image 、 Video etc.
   /4、 Character stream

IO Stream operation data
eg.           # Cover the original content
    >>> f=open("fa.txt","w")       
    >>> f
    <_io.TextIOWrapper name='fa.txt' mode='w' encoding='cp936'>
    >>> f.write("hello")
    5               #-------------- Returns the number of characters written
    >>> f.close()          # Write to characters to display

eg.            # Do not turn off the display of input
    >>> f=open("fa.txt","w")
    >>> f.write(" Da da da da da da da da ")
    12
    >>> f.flush()

eg.            # Do not overwrite the original content
    >>> f.flush()
    >>> f=open("fa.txt",mode="a")
    >>> f.write("dsfsdfd")
    7
    >>> f.close()