我的代码为什么不返回字典的平均值？

Question

    >>> get_average_club_count(P2C)
    1.6
    """
    average = 0
    summ = 0
    for key in person_to_clubs:
        summ = sum + len(person_to_clubs[key])
    average = sum / len(person_to_clubs)

我正在使用的字典：

当我尝试执行docstring示例时得到的回报：

    summ = sum + len(person_to_clubs[key])
builtins.TypeError: unsupported operand type(s) for +: 'builtin_function_or_method' and 'int'

Answer 1

sum是一个内置函数，因此不能将其用作变量名。命名summ也不是一个很好的解决方法，因为您容易混淆自己（就像我认为的那样）。也许total？

total = 0.0
for person in person_to_clubs:
    total += len(person_to_clubs[person])
return total / len(person_to_clubs)

Answer 2

我相信您在变量名中缺少了一个“ m”！

我会说正确的代码是：

def get_average_club_count(person_to_clubs: Dict[str, List[str]]) -> float:
    """Return the average number of clubs that a person in person_to_clubs
    belongs to.

    >>> get_average_club_count(P2C)
    1.6
    """
    average = 0
    summ = 0
    for key in person_to_clubs:
        summ = summ + len(person_to_clubs[key])
    average = summ / len(person_to_clubs)

错误来自以下事实：sum是Python中的内置函数，而summ是您定义的局部变量。