An n-gram is a sequence of n letters. For example, bol and old are the two 3-grams that occur in the string bold.

Use Python 3 Jupyter Notebook:

Write a function called count_ngrams() that counts the number of times each n-gram occurs in a string, with n specified by the user and with default value n = 1. Use dictionary for output.

Example usage:

count_ngrams("tortoise", n = 2)

{'to': 2, 'or': 1, 'rt': 1, 'oi': 1, 'is': 1, 'se': 1} # output