python语句的输出关键字是,指定end关键字后，为什么python3的print语句不刷新输出？...

from sys import argv, stdout as cout

from time import sleep as sl

print("Rewinding.......",end = '') # If end is given output isn't flushed. But why?

cout.flush()

for i in range(0,20):

sl(0.2)

print(".",end='',flush = True) #No output is printed if flush wasn't specified as true.

print("Done") #Output is by default flushed here

When I specified end and sleep, I noticed that output wasn't flushed until next print where it was by default flushed.

Why does this happen? I had to manually flush the output.

解决方案

In fact this is the default behavior of the underlying stdio functions.

When the output is to console, the stream will be automatically flushed when a newline is encountered, but not other characters.

If the output is not a console, then even newline won't trigger a flush.

If you want to make sure about flush, you can tell the print() explicitly:

print("Rewinding.......",end = '',flush=True)