The second argument of python replace function-CodePudding

I would like to sort words in roots, and then replace the sentence by each root. The below code throw me an error

TypeError: replace() argument 2 must be str, not list

def replace_words(roots, sentence):

    for word in sentence.split():
        matches = [root for root in roots if word.startswith(root)]
    #print(matches)
    
        if len(matches) >0:
           sentence = sentence.replace(word, sorted(matches, key=lambda x:len(x)))

    return sentence.strip()

But if we add [0] behind sorted( ), it will fix the error:

Looks like [0] converted the second argument of sorted function from list to string, but I really have trouble understanding what is the underlying process. Could anyone kindly explain it?

CodePudding user response：

You're overthinking the error...

Does it make sense if you write it like this?

sorted_roots = sorted(matches, key=lambda x:len(x))
sentence = sentence.replace(word, sorted_roots)

sorted() returns a list. str.replace() needs 2 string arguments, not a string, and a list.

By adding [0] to the end of sorted(), you've gotten the first element of the sorted list (the shortest root)