l=['a','b','c']
count=0
while 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的倆種使用方式
print(next(d_iter))
print(next(d_iter))
print(next(d_iter)) #迭代器d_iter沒(méi)有值的時(shí)候，會(huì)拋出異常：StopIteration
print(next(d_iter))

#下面是如何去除StopIteration異常
while True:
  try:   #使用try：去除異常
    print(next(d_iter))
  except StopIteration: #去除異常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 3
a=func()
print(next(a)) #next(a),會(huì)執(zhí)行到第一個(gè)yield結(jié)束，返回結(jié)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)
>>>
---->1
1
---->2
2
---->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))

#制作一個(gè)range函數(shù)
def range_it(start,stop,step=1):
  while stop > start:
    yield start
    start=start + step
for i in range_it(1,20,2):
  print(i)

import time
# 小練習(xí)：:tail -f access.log | grep '404'
def tail(filepath): #檢測(cè)是否有新的寫(xiě)入信息，如果有一條就給yield，作為函數(shù)的返回結(jié)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): #傳入tail檢測(cè)到新增加的行，然后打印出來(lái)這一行并賦值給line，再做判斷404，在就使用yield返回這一行
  for line in lines:
    # print(line)
    line=line.decode('utf-8')
    if pattern in line:
      yield line
lines=grep(tail('a.txt'),'404') #grep()函數(shù)執(zhí)行的結(jié)果返回的yield的值，給他賦值，
for line in lines:    #使用for去循環(huán)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')
#首先要做一個(gè)初始化的操作：也就是必須要先給yield傳入一個(gè)None的值。
print(e.send(None)) #next(e)
print(e.send('一桶水')) #給yield賦值一次，然后會(huì)執(zhí)行下面的代碼，然后循環(huán)到下一個(gè)yield停止
print(e.send('一盤(pán)骨頭'))