`python`定制类主要是实现特定功能，通过在类中定义特定的函数完成特定的功能。
class Student(object):
def __init__(self, name):
self.name =name student = Student("lilei")
print(student)
`实现定制类`
class Student(object):
def __init__(self, name):
self.name = name
def __str__(self):
return ("self name is %s" %(self.name)) student2 = Student("hanmeimei")
print(student2)
实现`__str__`函数，可以在print类对象时打印指定信息
通过实现`__iter__`和`__next__`同样可以使类对象产生可迭代序列，下面实现了`斐波那契数列`
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
f self.a > 30:
raise StopIteration()
return self.a
打印输出
for n in Fib():
print(n)
可以实现`__getitem__`函数,这样就可以按照索引访问类对象中迭代元素了。
class OddNum(object):
def __init__(self):
self.num = -1
def __iter__(self):
return self
def __next__(self):
self.num = self.num +2
if self.num > 10:
raise StopIteration()
return self.num def __getitem__(self,n):
temp = 1
for i in range(n):
temp += 2
return temp
for n in OddNum():
print(n) oddnum = OddNum()
print(oddnum[3])
可以进一步完善OddNum类的`__getitem__`函数，使其支持`切片处理`
def __getitem__(self, n):
if isinstance(n ,int):
temp =1
for i in range(n):
temp +=2
return temp
if isinstance(n, slice):
start = n.start
end = n.stop
if start is None:
start = 0
tempList = []
temp = 1
for i in range(end):
if i >= start:
temp += 2
tempList.append(temp)
return tempList
`print(oddnum[1:4])`
通过实现`__getattr__`函数，可以在类对象中没有某个属性时，自动调用`__getattr__`函数
实现`__call__`函数，可以实现类对象的函数式调用
def __getattr__(self,attr):
if attr == 'name':
return 'OddNum'
if attr == 'data':
return lambda:self.num
raise AttributeError('\'OddNum\' object has no attribute \'%s\'' %attr)
def __call__(self):
return "My name is OddNum!!"
只有在没有找到属性的情况下，才调用`__getattr__`，已有的属性不会在`__getattr__`中查找。
print(oddnum.name)
print(oddnum.data)
#没有func函数会抛出异常
#print(oddnum.func)
#可以直接通过oddnum()函数式调用
print(oddnum())
下面是廖雪峰官方网站上的一个链式转化例子，用到了这些特定函数
class Chain(object):
def __init__(self, path=''):
self.path = path
def __getattr__(self,attr):
return Chain('%s/%s'%(self.path, attr))
def users(self, users):
return Chain('%s/users/%s' %(self.path, users))
def __str__(self):
return self.path
__repr__ = __str__
print(Chain().users('michael').repos)
class Chain(object):
def __init__(self, path=''):
self.path = path
def __getattr__(self,attr):
return Chain('%s/%s'%(self.path, attr))
def __call__(self, param):
return Chain('%s/%s'%(self.path, param))
def __str__(self):
return self.path
__repr__ = __str__ print(Chain().get.users('michael').group('doctor').repos)
python同样支持`枚举`操作
from enum import Enum
Month = Enum('Month', ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'))
for name, member in Month.__members__.items():
print(name, '=>', member, ',', member.value)
from enum import Enum
Month = Enum('Month', ('Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec') )
for name, member in Month.__members__.items():
print(name, '=>', member, ',', member.value)
from enum import unique
@unique
class Weekday(Enum):
Sun = 0 # Sun的value被设定为0
Mon = 1
Tue = 2
Wed = 3
Thu = 4
Fri = 5
Sat = 6
for name , member in Weekday.__members__.items():
print(name, '=>', member, ',', member.value)我的微信公众号：