举个例子：

str1 = 'sunlightn'
f = str1.rfind("n", __start=1, __end=2)
print(f)

以上代码运行后出现：

"D:\Program Files\Python\Python37-32\python.exe" D:/demo/str_1.py
Traceback (most recent call last):
File "D:/demo/str_1.py", line 147, in
f = str1.rfind("n", __start=1, __end=2)
TypeError: rfind() takes no keyword arguments

Process finished with exit code 1

意思是 rfind()方法不接受关键字参数，而代码中又使用了关键字参数

修改为位置参数后正常运行

str1 = 'sunlightn'
f = str1.rfind("n", 1, 2)
print(f)

"D:\Program Files\Python\Python37-32\python.exe" D:/demo/str_1.py
-1

Process finished with exit code 0