如何为类对象创建自定义字符串表示形式？

Question

考虑这个课程：

class foo(object):

    pass

默认字符串表示形式如下所示：

>>> str(foo)

"<class '__main__.foo'>"

如何将此显示设为自定义字符串？

Answer 1

实现__str__()或__repr__()在类的元类中。class MC(type):&nbsp; def __repr__(self):&nbsp; &nbsp; return 'Wahaha!'class C(object):&nbsp; __metaclass__ = MCprint C使用__str__，如果你说的是可读的字串，使用__repr__了明确的表示。

Answer 2

class foo(object):&nbsp; &nbsp; def __str__(self):&nbsp; &nbsp; &nbsp; &nbsp; return "representation"&nbsp; &nbsp; def __unicode__(self):&nbsp; &nbsp; &nbsp; &nbsp; return u"representation"

Answer 3

如果您必须在第一个之间进行选择__repr__或者选择__str__第一个，则默认情况下在未定义时执行__str__调用__repr__。自定义Vector3示例：class Vector3(object):&nbsp; &nbsp; def __init__(self, args):&nbsp; &nbsp; &nbsp; &nbsp; self.x = args[0]&nbsp; &nbsp; &nbsp; &nbsp; self.y = args[1]&nbsp; &nbsp; &nbsp; &nbsp; self.z = args[2]&nbsp; &nbsp; def __repr__(self):&nbsp; &nbsp; &nbsp; &nbsp; return "Vector3([{0},{1},{2}])".format(self.x, self.y, self.z)&nbsp; &nbsp; def __str__(self):&nbsp; &nbsp; &nbsp; &nbsp; return "x: {0}, y: {1}, z: {2}".format(self.x, self.y, self.z)在此示例中，repr再次返回可以直接使用/执行的字符串，而str作为调试输出更有用。v = Vector3([1,2,3])print repr(v)&nbsp; &nbsp; #Vector3([1,2,3])print str(v)&nbsp; &nbsp; &nbsp;#Vector(x:1, y:2, z:3)