Keywise dictionary reduction operator.

dict-reduce.py

def dict_reduce(f, *dicts):
    """
    Apply a function f to the values of an iterable of dictionaries by key
    
    Gets a complete set of keys across all dictionaries, then, for each key,
    applies f to the list of values of each dictionary for that key.
    
    Args:
        f (function): a function that takes an iterable
        *dicts: an iterable of dictionaries
        
    Returns:
        a dictionary s.t. d[k] = f(d1[k], d2[k], d3[k]...) for all k
    """
    reduced_dict = {}
    key_sets = (set(d.keys()) for d in dicts)
    keys = set.union(*key_sets)
    for key in keys:
        values = (d[key] for d in dicts if key in d)
        reduced_dict[key] = f(*values)
    return reduced_dict