请问为什么我放在同一个文件夹下，用相对路径会显示No such file or directory: './test.txt'呀

f = open("./test.txt",'r')

content = f.readlines()

f1=open("./test1.txt","w")

for line in content:

    line=content[::-1]

    f1.write(line)

f1.close()

f.close()