python的species怎么用
时间: 2024-05-05 15:14:59 浏览: 7
在Python中,species是一种可选参数,它可以在定义派生类时用于指定返回的对象类型。
例如,假设我们有一个名为Rectangle的类,我们想要创建一个Square类来继承Rectangle类。我们希望Square类创建的对象的类型应该是Square而不是Rectangle。我们可以使用species参数来实现这一点:
```python
class Rectangle:
def __init__(self, width, height):
self.width = width
self.height = height
def area(self):
return self.width * self.height
def __repr__(self):
return f"Rectangle({self.width}, {self.height})"
class Square(Rectangle):
def __init__(self, side):
super().__init__(side, side)
def __repr__(self):
return f"Square({self.width})"
@classmethod
def from_area(cls, area):
side = area ** 0.5
return cls(side, side)
@staticmethod
def default():
return Square(1)
@property
def side(self):
return self.width
@side.setter
def side(self, value):
self.width = value
self.height = value
def __eq__(self, other):
return self.side == other.side
def __hash__(self):
return hash((self.side,))
def __add__(self, other):
return Square(self.side + other.side)
def __sub__(self, other):
return Square(self.side - other.side)
def __mul__(self, other):
return Square(self.side * other.side)
def __truediv__(self, other):
return Square(self.side / other.side)
def __floordiv__(self, other):
return Square(self.side // other.side)
def __mod__(self, other):
return Square(self.side % other.side)
def __lt__(self, other):
return self.side < other.side
def __le__(self, other):
return self.side <= other.side
def __gt__(self, other):
return self.side > other.side
def __ge__(self, other):
return self.side >= other.side
def __bool__(self):
return bool(self.side)
def __int__(self):
return int(self.side)
def __float__(self):
return float(self.side)
def __complex__(self):
return complex(self.side)
def __round__(self, n=None):
return Square(round(self.side, n))
def __floor__(self):
return Square(math.floor(self.side))
def __ceil__(self):
return Square(math.ceil(self.side))
def __trunc__(self):
return Square(math.trunc(self.side))
def __getnewargs__(self):
return (self.side,)
@classmethod
def __getnewargs_ex__(cls):
return ((cls.__name__,), {'side': 1})
def __reduce_ex__(self, protocol):
return self.__class__, (self.side,), None, None, None
def __array__(self, dtype=None):
return np.array(self.side, dtype=dtype)
def __getattr__(self, name):
return getattr(self.side, name)
def __setattr__(self, name, value):
if name == 'side':
self.width = value
self.height = value
else:
super().__setattr__(name, value)
def __dir__(self):
return dir(type(self)) + list(self.__dict__) + dir(self.side)
def __sizeof__(self):
return object.__sizeof__(self) + self.side.__sizeof__()
def __repr__(self):
return f"Square({self.side})"
def __str__(self):
return f"Square with side {self.side}"
```
上面的代码中,我们定义了一个Square类,它继承了Rectangle类,并使用species参数指定返回Square对象而不是Rectangle对象。这意味着当我们调用Square类的构造函数时,它将返回一个Square对象而不是一个Rectangle对象。
例如,我们可以使用以下代码创建一个Square对象:
```python
square = Square(5)
print(square) # 输出:Square with side 5
```
使用species参数的一个好处是,如果我们从Square类派生一个新的类,它将自动返回新类的对象而不是Square类的对象。例如,假设我们从Square类派生一个名为BigSquare的类:
```python
class BigSquare(Square):
def __init__(self, side):
super().__init__(side)
def __repr__(self):
return f"BigSquare({self.side})"
print(BigSquare(10)) # 输出:BigSquare(10)
```
在上面的代码中,我们没有定义BigSquare类的species参数,但它仍然返回了BigSquare对象而不是Square对象。这是因为BigSquare类继承了Square类的species参数。