Transforming a string in a list

How can I transforms strings in list return a list consisting the elements of strings and the lengths of strings? Just like add_sizes([str]) -> [(str, int)]

Here is what I did:

def add_sizes(strings):
    for i in strings:
        return [(i, (len(i)))]

but this only works for one string, what should I do if I have more than one string?