Sys. stdout. write and print and sys. stdout. flush, sys. stdout. write

Sys. stdout. write and print and sys. stdout. flush, sys. stdout. write

1. Read the official documentation first.

 1 """ 2 sys.stdout.write(string) 3 　　Write string to stream. 4 　　Returns the number of characters written (which is always equal to the length of the string). 5  6 print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False) 7 　　Prints the values to a stream, or to sys.stdout by default. 8  9 　　Optional keyword arguments:10 　　file:  a file-like object (stream); defaults to the current sys.stdout.11 　　sep:   string inserted between values, default a space.12 　　end:   string appended after the last value, default a newline.13 　　flush: whether to forcibly flush the stream.14 """

We can see that

① Sys. stdout. write writes str to the stream. It is not blocked and will not default end = '\ n' like print'

② Sys. stdout. write can only output one str, while print can output multiple str, and the default sep = ''(one space)

③ Print. The default value is flush = False.

④ Print can also directly write the value to file

1 import sys2 f = open('test.txt', 'w')3 print('print write into file', file=f)4 f.close()

 

2. sys. stdout. flush ()

1 flush() 2     method of _io.TextIOWrapper instance3     Flush write buffers, if applicable.4     5     This is not implemented for read-only and non-blocking streams.

Flush indicates a refresh. There is a buffer in the output of print and sys. stdout. write.

For example, if you want to output a string to the file, it is written into the memory first (Because print defaults to flush = False, and flush is not executed manually). There is nothing to open the file directly before closing the file, if you execute a flush command, you will have it.

1 import time2 import sys3  4 for i in range(5):5     print(i)6     sys.stdout.flush()7     time.sleep(1)

When the code is executed on the terminal, a number is output in one second. However, if flush is commented out, 01234 will be output once in 5 seconds.