python 笔记——生成器和迭代器

#-*- coding:utf-8 -*-

a=[1,2,3,4]
for i,j in enumerate(a):
    print i,j

'''只有ij时，'''

a=[1,2,3,4]
for i in enumerate(a):
    print i
'''只有i 时，'''

dic={1:'a',2:'c','d':4}
for i in enumerate(dic):
    print i
    '''是字典时，对应得是key'''

b=[1,2,4,5,6,7,]
for index,i in enumerate(b):

    print index,i
    b[index]+=1
print(b)
print('jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj')

c=[1,2,4,6,7,8]
c=map(lambda x:x+1,c)
for i in c:
    print i
print (type(c))
'''产生的是一个list所以要循环打印，'''
l=[j+1 for j in range(10)]
print l
print (type(l))
'''产生的是一个list生产序列'''

g=(j+1 for j in range(10))
print g     #这里这句打印的是g生成器的内存地址
print (type(g))
#print g.next()调用生成器的.next()可以显示生成器里的计算出来的元素，
# 但一次调用只能显示一个元素，可以采用for循环来显示所有元素.可迭代对象
for i in g:
    print i

print('jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj')

'''斐波那函数的编程
def fib(max):
    n,a,b=0,0,1
    while n<max:
        print b
        a,b=b,a+b
        n+=1

fib(10)
'''
def pluse (a,b):
    print (a+b)
def fib(max):
    n, a, b = 0, 0, 1
    while n < max:
        yield b
        a, b = b, a + b
        n += 1

data=fib(10)
print (data.next())
print (data.next())
pluse(100,200)
print (data.next())
print ('hahahhhahhahha')
print (data.next())
print (data.next())
print (data.next())

凡是可作用于for循环的对象都是Iterable类型；

凡是可作用于next()函数的对象都是Iterator类型，它们表示一个惰性计算的序列；

集合数据类型如list、dict、str等是Iterable但不是Iterator，不过可以通过iter()函数获得一个Iterator对象。

Python的for循环本质上就是通过不断调用next()函数实现的

#-*- coding:utf-8 -*-
from collections import Iterator
print (isinstance((),Iterator))
print (isinstance([],Iterator))
print (isinstance('adf',Iterator))
print (isinstance([i *2 for i in range(10)],Iterator))

print (isinstance((i *2 for i in range(10)),Iterator))#是生成器

#可以直接用于for循环的对象为可迭代对象
print ('jjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjjj')

from collections import Iterable
print (isinstance((),Iterable))
print (isinstance([],Iterable))
print (isinstance({},Iterable))
print (isinstance('adf',Iterable))
print (isinstance([i *2 for i in range(10)],Iterable))
print (isinstance((i *2 for i in range(10)),Iterable))#是生成器
#可以直接被next()函数调用并不断返回下一个值得对象称为迭代器

l=[1,2,6,8,9] 
It=iter(l) 
print It 
print (isinstance(It,Iterator))