Uppercase every other word in a string using split/join

I have a string:

string = "Hello World" 

That needs changing to:

"hello WORLD" 

Using only split and join in Python.

Any help?

string = "Hello World" 

split_str = string.split()

Can’t then work out how to get first word to lowercase second word to uppercase and join

>Solution :

string = "Hello World"
split_str  = string.split()
print(' '.join([split_str[0].lower(),split_str[1].upper()]))