字符串格式化与.format()

import time
scale=10
print("{:-^18}".format("执行开始"))
for i in range(scale+1):
    a="*"*i
    b="."*scale
    scale -= 1
    c=i*scale
    print('{:^3}%[{}->{}]'.format(c,a,b))
    time.sleep(0.01)
print("{:-^18}".format("执行结束"))