8.11 简化数据结构的初始化.pdfVIP

8.11 简化数据结构的初始化 问题 你写了很多仅仅⽤作数据结构的类，不想写太多烦⼈的 __init__() 函数 解决⽅案 可以在⼀个基类中写⼀个公⽤的 __init__() 函数： import math class Structure1: # Class variable that specifies expected fields _fields = [] def __init__(self *args): if len(args) != len(self._fields): raise TypeError(Expected {} arguments.format(len(sel # Set the arguments for name value in zip(self._fields args): setattr(self name value) 然 使你的类继承⾃这个基类: # Example class definitions class Stock(Structure1): _fields = [name shares price] class Point(Structure1): _fields = [x y ] class Circle(Structure1): _fields = [radius] def area(self): return math.pi * self.radius ** 2 使⽤这些类的⽰例： s = Stock(ACME 50 91.1) p = Point(2 3) c = Circle(4 .5) s2 = Stock(ACME 50) Traceback (most recent call last): File stdin line 1 in module File structure.py line 6 in __init__ raise TypeError(Expected {} arguments.format(len(self._f TypeError: Expected 3 arguments 如果还想⽀持关键字参数，可以将关键字参数设置为实例属性： class Structure2: _fields = [] def __init__(self *args **kwargs): if len(args) len(self._fields): raise TypeError(Expected {} arguments.format(len(sel # Set all of the positional arguments for name value in zip(self._fields args): setattr(self name value) # Set the remaining keyword arguments for name in self._fields[len(args):]: setattr(self name kwargs.pop(name)) # Check for any remaining unknown arguments if kwargs: raise TypeError(Invalid argument(s): {}.format( .j # Example use if __name__ == __main__: class Stock(Structure2): _fields = [name shares price] s1 = Stock(ACME 50 91.1) s2 = Stock(ACME 50 price=91.1) s3 = Stock(ACME shares=50 price=91.1) # s3 = Stock(ACME shares=50 price=91.1 aa=1)