class Student(object):
pass
s = Student()
s.name = 'Michael'
print(s.name)
def set_age(self, age):
self.age = age
from types import MethodType
s.set_age = MethodType(set_age, s) #给实例绑定一个方法
s.set_age(25)
print(s.age)
#注意给一个实例绑定的方法对于另一个实例是不起作用的
s2 = Student() #创建新的实例
#为了给所有的实例都绑定方法，可以给class绑定方法
def set_score(self, score):
self.score = score
Student.set_score = set_score
s.set_score(100)
print(s.score)
s2.set_score(99)
print(s2.score)
#如果我们想限制类的属性,比如，只允许对Student实例添加name和age属性
#__slots__定义的属性仅对当前类实例起作用，对继承的子类是不起作用的：
#除非在子类中也定义__slots__，这样，子类实例允许定义的属性就是自身的__slots__加上父类的__slots__。
class Student(object):
__slots__ = ('name', 'age')
s = Student()
s.name = 'Michael'
s.age = 25
#s.score = 99 #因为__slots__('name', 'age')限制Student实例只能添加name和age属性
class Teacher(object):
def __init__(self, name, subject):
self.name = name
self.subject = subject
t = Teacher('wangxin', 'math')
print(t.name)
print(t.subject)
class Student(object):
def __init__(self, name):
self.name = name
print(Student('Michael'))
class Student(object):
def __init__(self, name):
self.name = name
def __str__(self):
return 'Student object (name:%s)' %self.name
__repr__ = __str__
print(Student('Michael'))
class Fib(object):
def __init__(self):
self.a, self.b = 0, 1
def __iter__(self):
return self
def __next__(self):
self.a, self.b = self.b, self.a+self.b
if self.a > 100000:
raise StopIteration();
return self.a
for n in Fib():
print(n)
#要表现得像list那样按照下标取出元素，需要实现__getitem__()方法：
class Fib(object):
def __getitem__(self, n):
a, b = 1, 1
for x in range(n):
a, b = b, a+b
return a
f = Fib()
print(f[0])
print(list(range(100))[5:10])
class Fib(object):
def __getitem__(self, n):
if isinstance(n, int):
a, b = b, a+b
return a
if isinstance(n, slice):
start = n.start
stop = n.stop
if start is None:
start = 0
a, b = 1, 1
L = []
for x in range(stop):
if x >= start:
L.append(a)
a, b = b, a+b
return L
f = Fib()
print('---------')
print(f[0:5])
