How can I assert the values of my dict when they are in a list

My_dict = {'chr7': [127479365, 127480532], 'chr8': [127474697, 127475864], 'chr9': [127480532, 127481699]}

The code to assert this

assert all(isinstance(values, int) for values in My_dict.values()),"The values of the dict are not interger"

You actually want to check values of your dict are lists and that all of their elements are integers.

assert all(isinstance(value, list) and all(isinstance(el, int) for el in value)for value in data_loaded.values()
), "Values of the dictionnary aren't lists of integers"