Python中字符串转换大小写的方法有三种：
s = "hello" s_upper = s.upper() print(s_upper) # 输出：HELLO
s = "HELLO" s_lower = s.lower() print(s_lower) # 输出：hello
s = "hello world" s_title = s.title() print(s_title) # 输出：Hello World
