python中\r的意义及用法

def print(self, *args, sep=' ', end='\n', file=None): # known special case of print
    """
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)
    
    Prints the values to a stream, or to sys.stdout by default.
    Optional keyword arguments:
    file:  a file-like object (stream); defaults to the current sys.stdout.
    sep:   string inserted between values, default a space.
    end:   string appended after the last value, default a newline.
    flush: whether to forcibly flush the stream.
    """

print("Dream", "it", "possible", sep="-",end="/")
print("Big big world")
#########结果如下################
Dream-it-possible/Big big world
Process finished with exit code 0

# 显示倒计时
import time
for i in range(10):
    print("\r离程序退出还剩%s秒" % (9-i), end="")
    time.sleep(1)

import time
lst = ["\\", "|", "/", "———"]
for i in range(20):
    j = i % 4
    print("\r" + lst[j], end="")
    time.sleep(0.2)

# 进度条功能
import time

for i in range(10):
    print("\r" + "■"*i, sep="", end="")
    time.sleep(0.2)
print("\n下载完成")

import time
s = "枝上柳绵吹又少，天涯何处无芳草"
l = len(s)
for i in range(l):
    print("\r" + s[:l-1-i] + "|", end="")
    time.sleep(0.15)