Count-words-in-Python

Implement a function count_words() in Python that takes as input a string s and a number n, and returns the n most frequently-occuring words in s. The return value should be a list of tuples - the top n words paired with their respective counts [(<word>, <count>), (<word>, <count>), ...], sorted in descending count order. You can assume that all input will be in lowercase and that there will be no punctuations or other characters (only letters and single separating spaces). In case of a tie (equal count), order the tied words alphabetically. E.g.: print count_words("betty bought a bit of butter but the butter was bitter",3)