迭代器

迭代器

可迭代对象

    数字类型不是一个可迭代对象

from collection import Iterable
# 判断是否为可迭代对象,返回True则可迭代
isinstance([11,22,33],Iterable)

 实现一个可迭代对象

from collections import Iterable

class Classmate(object):
    def __init__(self):
        self.names = list()
    def add(self,name):
        self.names.appdend(name)
    def __iter__(self):
        """此方法能把实例化的对象变成一个可迭代对象"""
        return ClassIterator(obj)

class ClassIterator(object):
    def __init__(self，obj):
        self.obj = obj
    def __iter__(self)：
        pass
    def __next__(self):
        return obj.names[current_num]
        
classmate = Classmate()

classmate.add("老王")

classmate.add("老赵") 

classmate.add("老章")

for name in classmate:
    print(names)
    print("判断是否为迭代对象"，isinstance(classmate,Iterable))

#用iter方法调用实例化后的对象
classmate_iterator = iter(classmate)
    print("判断是否为迭代器"，isinstance(classmate_iterator,Iterator))
print(next(classmator_iterator))

完善迭代器

from collections import Iterable

class Classmate(object):
    def __init__(self):
        self.names = list()
    def add(self,name):
        self.names.appdend(name)
    def __iter__(self):
        """此方法能把实例化的对象变成一个可迭代对象"""
        return ClassIterator(obj)

class ClassIterator(object):
    def __iter__(self，obj):
        self.obj = obj
        self.currentnum = 0
    def __next__(self):
        if self.current_num < len(self.obj.names):
            set = self.obj.names[self.current_num]
            self.current_num += 1
            return ret
        else:
             raise StopIteration
        
classmate = Classmate()

classmate.add("老王")

classmate.add("老赵") 

classmate.add("老章")

for name in classmate:
    print(names)
    print("判断是否为迭代对象"，isinstance(classmate,Iterable))

#用iter方法调用实例化后的对象
classmate_iterator = iter(classmate)
    print("判断是否为迭代器"，isinstance(classmate_iterator,Iterator))
print(next(classmator_iterator))

简便写法

from collections import Iterable

class Classmate(object):
    def __init__(self):
        self.names = list()
        self.current_num = 0

    def add(self,name):
        self.names.append(name)

    def __iter__(self):
        """此方法能把实例化的对象变成一个可迭代对象"""
        return self

    def __next__(self):
        if self.current_num < len(self.names):
            ret = self.names[self.current_num]
            self.current_num += 1
            return ret
        else:
             raise StopIteration

classmate = Classmate()

classmate.add("老王")

classmate.add("老赵")

classmate.add("老章")

#for name in classmate:
   # print(names)
#print("判断是否为迭代对象",isinstance(classmate,Iterable))

#用iter方法调用实例化后的对象
classmate_iterator = iter(classmate)
#print("判断是否为迭代器",isinstance(classmate_iterator,Iterator))

#print(next(classmator_iterator))
for name in classmate:
    print(name)

迭代器的应用

不用迭代器的实现方法

nums = list()
a = 0
b = 1
i = 0

while i < 10:
    nums.append(a)
    a,b = b,a+b
for num in nums：
    print(num)

用迭代器实现方法

from collections import Iterable

class Fibonacci(object):
    def __init__(self):
        self.names = list()
        self.current_num = 0

    def add(self,name):
        self.names.append(name)

    def __iter__(self):
        """此方法能把实例化的对象变成一个可迭代对象"""
        return self

    def __next__(self):
        if self.current_num < len(self.names):
            ret = self.names[self.current_num]
            self.current_num += 1
            return ret
        else:
             raise StopIteration

fibo = Fibonacci()
Fibonacci.add("老张")
Fibonacci.add("老刘")
Fibonacci.add("老王")
for num in fibo:
    print(name)