python 类的字符串显示

class Pair:
def init(self, x, y):
self.x = x
self.y = y

def __repr__(self):
    return 'Pair({0.x!r}, {0.y!r})'.format(self)

def __str__(self):
    return '({0.x!s}, {0.y!s})'.format(self)