如何从字符串中删除单词？

str = "hello world"
word_list = str.split()
del word_list[1]
new_str = " ".join(word_list)
print(new_str) # 输出 "hello world"

str = "hello world"
new_str = str.replace("world", "hello")
print(new_str) # 输出 "hello hello"

import re
str = "hello world"
new_str = re.sub("world", "hello", str)
print(new_str) # 输出 "hello hello"