.format outside of strings

Hello, So I am almost done with Python Collections and a thought occurred to me. I had just done a four step code challenge all about dictionaries and returning a specific key, with a specific list, at a specific time (when the teacher has the most classes that's who gets returned). And it took 4 functions and I don't even know how many lines of code, but now I am learning about tuples and I realize you can just make a string with a few {} and .format and get the same results as the dictionary code challenge. So why didn't the code challenge just ask us to use {} to return the specific key with a specific list? Can you even use {} and .format outside of strings? For example can I do

return {}: {}.format(dictionary[key], dictionary.value())

or does that .format only work with strings? If so why? (I realize that the single line of code I gave wouldn't have completed the whole code challenge alone, but it would have cut off a few lines of code and save some time)