Python迭代器与生成器用法实例分析

l=['a','b','c']count=0while count <len(l):  print(l[count])  count+=1

str   name='lqx' name.__iter__list  l=[1,2,3]  l.__iter__tuple  t=(1,2,3)  t.__iter__dict  d={'name':'lqx','age':18,'sex':'male'} d.__iter__set   s={'a','b','c'} s.__iter__file  f=open('a.txt','w',encoding='utf-8')  f.__iter__

d={'name':'egon','age':18,'sex':'male'}d_iter=d.__iter__() #使用iter之后，生成的d_iter是迭代器print(d_iter,type(d_iter))print(d_iter.__next__()) #next的俩种使用方式print(next(d_iter))print(next(d_iter))print(next(d_iter)) #迭代器d_iter没有值的时候，会抛出异常：StopIterationprint(next(d_iter))

#下面是如何去除StopIteration异常while True:  try:   #使用try：去除异常    print(next(d_iter))  except StopIteration: #去除异常StopIteration    break

d={'name':'lqx','age':19,'sex':'male'}for k in d:  print(k)

l=[1,2,3,4,5]l_iter=l.__iter__()print(next(l_iter))print(next(l_iter))print(next(l_iter))print(len(l_iter))  #TypeError: object of type 'list_iterator' has no len()

def func():  print('---->1')  yield 1  print('---->2')  yield 2  print('---->3')  yield 3a=func()print(next(a)) #next(a),会执行到第一个yield结束，返回结果是yield后面的返回值next(a)next(a)

g=func()res1=next(g)print(res1)res2=next(g)print(res2)res3=next(g)print(res3)>>>---->11---->22---->3

obj=range(1,1000000000000,2)obj_iter=obj.__iter__()print(next(obj_iter))print(next(obj_iter))print(next(obj_iter))print(next(obj_iter))

#制作一个range函数def range_it(start,stop,step=1):  while stop > start:    yield start    start=start + stepfor i in range_it(1,20,2):  print(i)

import time# 小练习：:tail -f access.log | grep '404'def tail(filepath): #检测是否有新的写入信息，如果有一条就给yield，作为函数的返回结果。  with open(filepath,'rb') as f:    f.seek(0,2)    while True:      line=f.readline()      if line:        yield line      else:        time.sleep(0.05)def grep(lines,pattern): #传入tail检测到新增加的行，然后打印出来这一行并赋值给line，再做判断404，在就使用yield返回这一行  for line in lines:    # print(line)    line=line.decode('utf-8')    if pattern in line:      yield linelines=grep(tail('a.txt'),'404') #grep()函数执行的结果返回的yield的值，给他赋值，for line in lines:    #使用for去循环取出lines中的值  print(line)

def eater(name):  print('%s ready to eat' %name)  food_list=[]  while True:    food=yield food_list    food_list.append(food)    print('%s start to eat %s' %(name,food))e=eater('alex')#首先要做一个初始化的操作：也就是必须要先给yield传入一个None的值。print(e.send(None)) #next(e)print(e.send('一桶水')) #给yield赋值一次，然后会执行下面的代码，然后循环到下一个yield停止print(e.send('一盘骨头'))