为什么在这个Python程序中会出现TypeError？

此代码给出了以下错误：
类型错误：列表索引必须是整数或切片，而不是str
我如何解决这个问题？如果我们调试：

# I'm trying to make a Zipf's Law observation using a dictionary that stores every word, and a counter for it. I will later sort this from ascending to descending to prove Zipf's Law in a particular text. I'm taking most of this code from Automate the Boring Stuff with Python, where the same action is performed, but using letters instead.
message = 'the of'
words = message.split()
wordsRanking = {}
for i in words:
    wordsRanking.setdefault(words[i], 0)
    wordsRanking[i] += 1   
print(wordsRanking)    

结果是：

message = 'the of'
words = message.split()
wordsRanking = {}
for i in words:
    print(i) ### add this
    wordsRanking.setdefault(words[i], 0)
    wordsRanking[i] += 1   
print(wordsRanking)   

---

因为我是一个词，不是索引；Python for循环在元素上迭代。已经回答的许多问题可以帮助您。只需在搜索栏中键入错误消息

the ## this is what printed. and word[i] is now equal to word["the"]. that raise an error
Traceback (most recent call last):
  File "C:\Users\Dinçel\Desktop\start\try.py", line 6, in <module>
    wordsRanking.setdefault(words[i], 0)
TypeError: list indices must be integers or slices, not str

message = 'the of'
words = message.split()
wordsRanking = {}
for i in words:
    wordsRanking.setdefault(i, 0)
    wordsRanking[i] += 1   
print(wordsRanking)