字典中字符串和缺失值的平均值(python)

def calculate_average(dictionary):
    total = 0
    count = 0

    for key, value in dictionary.items():
        if isinstance(value, str) or value is None:
            continue
        total += value
        count += 1

    if count > 0:
        average = total / count
        return average
    else:
        return None