在Python中實現一個點類

Question

所以我試圖實現一個點類，它創建一個點，然後旋轉，縮放和轉換點。這是我目前寫的。

class Point: 
    ''' 
     Create a Point instance from x and y. 
    ''' 
    def __init__(self, x, y): 
     self.x = 0 
     self.y = 0 

    ''' 
     Rotate counterclockwise, by a radians, about the origin. 
    ''' 
    def rotate(self, a): 
     self.x0 = math.cos(this.a) * self.x - math.sin(this.a) * self.y 
     self.y0 = math.sin(this.a) * self.x + math.cos(this.a) * self.y 

    ''' 

     Scale point by factor f, about the origin. 
    Exceptions 
     Raise Error if f is not of type float. 
    ''' 
    def scale(self, f): 
     self.x0 = f * self.x 
     self.y0 = f * self.y 

    ''' 
     Translate point by delta_x and delta_y. 
    Exceptions 
     Raise Error if delta_x, delta_y are not of type float. 
    ''' 
    def translate(self, delta_x, delta_y): 
     self.x0 = self.x + delta_x 
     self.y0 = self.y + delta_y 

    ''' 
     Round and convert to int in string form. 
    ''' 
    def __str__(self): 
     return int(round(self.x)) 

此代碼中的某些內容正在生成錯誤。現在我還沒有實現錯誤捕捉和我有在頂部

class Error(Exception): 
    def __init__(self, message): 
     self.message = message 

錯誤的方法，但我將如何捕捉錯誤，如果某個變量是float類型呢？

這裏的if語句我使用的一個：

def __init__(self, x, y): 
     if not isinstance(x, float): 
      raise Error ("Parameter \"x\" illegal.")   
      self.x = x 
      self.y = y 
     if not isinstance(y, float): 
      raise Error ("Parameter \"y\" illegal.") 
      self.x = x 
      self.y = y 

但是，這讓我的縮進錯誤。那麼，我怎樣才能打印出一個錯誤信息，說明哪個變量導致了問題？

Answer 1

如果該變量不是浮點數，您將得到一個TypeError。你幾乎可以像這樣「捕捉」這些錯誤;

try: 
    pass # your stuff here. 
except e as TypeError: 
    print e # this means a type error has occurred, type is not correct. 

另外，這將是值得閱讀的檢查正確的類型在開始assert; https://wiki.python.org/moin/UsingAssertionsEffectively

Answer 2

如果你想提高一個例外，它做了點的初始化：

def __init__(self, x, y): 
    if not isinstance(x, float) or not isinstance(y, float): 
     raise Error("Point's coordinates must be floats.") 
    self.x = x 
    self.y = y 

或轉換座標浮動：

def __init__(self, x, y): 
    self.x = float(x) 
    self.y = float(y)