Python定制类

1.__str__

class Student(object):

    def __init__(self, name):
        self._name = name

m = Student("michael")
print m

<__main__.Student object at 0x0000000003280EF0>

为了使print类的结果格式更加方便阅读

重写__str__(self)

class Student(object):

    def __init__(self, name):
        self._name = name

    def __str__(self):
        return "Student Name is %s !"% self._name

m = Student("michael")
print m

Student Name is michael !

__repr__类似与__str__，不同的__repr__主要运用与开发者交互方面

2.__iter__

将类变为可迭代的类型

class Fib(object):
    def __init__(self):
        self.a = 0
        self.b = 1

    def __iter__(self):
        return self

    def next(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a > 100:
            raise StopIteration()
        return self.a

for n in Fib():
    print n

3.__getitem__

用于迭代的时候，能用数组下标访问其中的变量

class Fib(object):
    def __init__(self):
        self.a = 0
        self.b = 1

    def __iter__(self):
        return self

    def next(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a > 100:
            raise StopIteration()
        return self.a

    def __getitem__(self, item):
        for i in range(item):
            self.a, self.b = self.b, self.a + self.b
        return self.a

print Fib()[11]

4.__getattr__

直接上例子：

class Person(object):
    def __init__(self):
        self.name = "Michael"

    def __getattr__(self, item):
        if item == "age":
            self.age = 22
            return self.age

m = Person()
print m.__getattr__("age")

附上一个动态生成路径的代码

class Clain(object):
    def __init__(self, path=""):
        self._path = path

    def __getattr__(self, item):
        return Clain("%s/%s"%(self._path, item))

    def __str__(self):
        return self._path

print Clain().usr.bin.env.python

/usr/bin/env/python

5.__call__

直接调用实例

上个例子：

class Person(object):
    def __init__(self):
        self.name = "Michael"

    def __call__(self, *args, **kwargs):
        print "My name is %s" % self.name

m = Person()
m()

My name is Michael

附：__getattr__ 和 __call__ 联合调用

class Clain(object):
    def __init__(self, path=""):
        self._path = path

    def __getattr__(self, item):
        return Clain("%s/%s"%(self._path, item))

    def __str__(self):
        return self._path

    def __call__(self, *args, **kwargs):
        for i in args:
            self._path = "%s/%s" % (self._path, i)
        return Clain(self._path)

print Clain().usr("Michael").bin.env.python

/usr/Michael/bin/env/python