python3 error: TypeError: must be str, not list

def make_pizza(*toppings):
    for j in range(0,len(toppings)):
        print(str(j)  + toppings[j])
list1 = ['s1','s2','s3','s4']
list2 = ['s3','s45','s4','s5']
make_pizza(list1,list2)    
make_pizza('sdf','asdf','asdf','asdf')

运行结果出现错误如下：

r@r:~/python$ python3 1.py
Traceback (most recent call last):
  File "1.py", line 6, in <module>
    make_pizza(list1,list2)    
  File "1.py", line 3, in make_pizza
    print(str(j)  + toppings[j])
TypeError: must be str, not list

The key is that in the print() brackets, the type connected by the plus sign must be str. Solid must convert the list to str

There must be a non-str type object where str is needed.

Solution: forced conversion to str