python面向对象举例

class Progression:
    """迭代地产生数列，默认产生 0, 1, 2, ..."""

    def __init__ (self, start=0):
        """初始化数列第一个值"""
        self._current = start

    def _advance(self):
        """更新数据当前值为新值，此方法应该被继承类重写"""
        self._current += 1 

    def __next__(self):
        """返回下一个元素, 或抛出StopIteration异常"""
        if self._current is None: 
            raise StopIteration()
        else:
            answer = self._current    # 返回当前值
            self._advance()    # 准备下次的返回值
            return answer

    def __iter__(self):
        """按常规，返回自己作为迭代器"""
        return self

    def print_progression(self, n):
        """打印前n个数列"""
        print(' '.join(str(next(self)) for j in range(n)))

if __name__ == "__main__":
    print('默认数列：')
    pro = Progression()
    pro.print_progression(10)

    print('首项为3的数列：')
    pro = Progression(start=3)
    pro.print_progression(10)

from progression import Progression

class ArithmeticProgression(Progression):
    """等差列数"""

    def __init__ (self, increment=1, start=0):
        """初始化
        increment:公差
        start:首项
        """
        super().__init__(start)      # 初始化基类
        self._increment = increment

    def _advance(self):              # 重写基类方法
        """增加公差，得到下一个值"""
        self._current += self._increment

if __name__ == "__main__":
    print('默认等差数列：')
    pro = ArithmeticProgression()
    pro.print_progression(10)
    
    print('首项为1，公差为3的等差数列：')
    pro = ArithmeticProgression(start=1,increment=3)
    pro.print_progression(10)

from progression import Progression

class GeometricProgression(Progression):
    """几何数列/等比数列"""

    def __init__ (self, base=2, start=1):
        """初始化

        base：等比数列的公比
        start：数据首项，默认为1
        """
        super().__init__(start)
        self._base = base

    def _advance(self):   # 重写基类方法
        """乘以公比，得到下一个元素"""
        self._current *= self._base

if __name__ == "__main__":
    print('默认等比列数:')
    pro = GeometricProgression()
    pro.print_progression(10)

    print('首项为5，公比为2的等比数列：')
    pro = GeometricProgression(start=5,base=2)
    pro.print_progression(10)

from progression import Progression

class FibonacciProgression(Progression):
    """斐波纳契数列"""

    def __init__ (self, first=0, second=1):
        """初始化
        first:第一元素
        second:第二元素
        """
        super().__init__(first)    # 初始化基类
        self._prev = second - first

    def _advance(self):    # 重写基类方法
        """后一个元素，等于前两个元素之和"""
        # temp = self._current
        # self._current = self._prev + self._current
        # self._prev = temp
        self._prev, self._current = self._current, self._prev + self._current

if __name__ == "__main__":
    print('默认斐波纳契数列：')
    pro = FibonacciProgression()
    pro.print_progression(10)

    print('前两位为3和4的斐波纳契数列：')
    pro = FibonacciProgression(first=3,second=4)
    pro.print_progression(10)