合并两个文件成一个新文件

问题遇到的现象和发生背景

问题相关代码，请勿粘贴截图

运行结果及报错内容

我的解答思路和尝试过的方法

我想要达到的结果

有两个文件testfile1.txt和testfile2.txt，要求把这两个文件中的内容合并保存到一个新文件testfie3.txt中，并输出到屏幕

filename_3 = 'testfile3.txt'

with open('testfile1.txt') as filename_1:
    contents_1 = filename_1.read()

with open('testfile2.txt')    as filename_2:
    contents_2 = filename_2.read()

contents = f"{contents_1}\n{contents_2}"

with open(filename_3,'w') as file_object:
    file_object.write(contents)

try:
    with open('testfile3.txt')    as f:
        contents_3 = f.read()
except FileNotFoundError:
    print(f"Sorry,the file {filename_3} does not exist.")
else:
    print(contents_3)

with open("testfile1.txt") as f:
con1=f.read()
with open("testfile2.txt") as f:
con2=f.read()

with open("testfile3.txt",'w') as f:
f.write(con1+'\n' + con2)

print(con1+'\n'+ con2)

这问题你也问！！！！