Python - 无法重载工作

Question

总之，我已经这样做了几天了，但仍然无法让这种重载发挥作用。

Error:
    setA: {-10,-8,3,5,10,17,20}
    intSet.len(setA):
    TypeError: __len__() takes exactly 2 arguments (1 given)

代码:

class intSet(object):
    """An intSet is a set of integers
    The value is represented by a list of ints, self.vals.
    Each int in the set occurs in self.vals exactly once."""

    def __init__(self):
        """Create an empty set of integers"""
        self.vals = []

    def insert(self, e):
        """Assumes e is an integer and inserts e into self""" 
        if not e in self.vals:
            self.vals.append(e)

    >>>>>> more methods left out for brevity <<<<<<<<<<

    def __len__(self, s):
        """ Returns the length of the string provided"""
        return len(s)

任何帮助将不胜感激...

Answer 1

__len__ 魔术方法不接受额外的参数。你的代码应该是

class IntSet(object):
"""An intSet is a set of integers
The value is represented by a list of ints, self.vals.
Each int in the set occurs in self.vals exactly once."""

def __init__(self):
    """Create an empty set of integers"""
    self.vals = []

>>>>>> more methods left out for brevity <<<<<<<<<<

def __len__(self):
    """Returns the number of elements in this set"""
    return len(self.vals)

然后在您的代码中以这种方式使用它

myset = IntSet()
print 'My set contains ', len(myset)
myset.insert(9)
myset.insert(10)
print 'My set contains ', len(myset)
myset.insert(9)
print 'My set contains ', len(myset)