from typing import Dict, List

def letter_counts(s: str) -> Dict[str, int]:
    """Return a dictionary mapping the characters in s to the 
    number of times each letter appeas in s.
    
    (another option for docstring description:)
    Return a dictionary where the keys are the characters in s
    and the values are the number of times each characters appears in s.
    
    Do not use str.count().
    
    >>> letter_counts('abc')
    {'a': 1, 'b': 1, 'c': 1}
    >>> letter_counts('www2')
    {'w': 3, '2': 1}
    """
    # Using dictionaries as accumulators
    
    # Create a dictionary to accumulate to
    counts = {}
    
    # Iterate over the characters in s
    for char in s:
        # if we don't find the keys in counts
        if not (char in counts.keys()):
            # create the key in counts and set the value to 1
            counts[char] = 1
        else:
            # add 1 to the value for that key
            counts[char] = counts[char] + 1
            
    return counts