def sum_dicts(dict1={}, dict2={}):
    """
    Merges to dictionaries. If they share keys, their values will be summed.\n
    Values should be numbers, otherwise results might be weird.

    Parameters
    ----------
    dict1 : \n
    dict2 : 

    Returns
    -------
    `dict` : Merged dictionary with all keys and summed values.
    """
    new_dict = dict1.copy()
    dict1_keys = dict1.keys()
    # merge dictionaries
    new_dict.update(dict2)
    all_keys = new_dict.keys()
    dict2_keys = dict2.keys()

    for key in all_keys:
        if key in dict1_keys and key in dict2_keys:
            new_dict[key] = dict1[key] + dict2[key]
    return new_dict