迭代器 可迭代對象:可迭代對象實現了__iter__方法，該方法返回一個迭代器對象。 迭代器: 那麼什麼迭代器呢？它是一個帶狀態的對象，他能在你調用next()方法的時候返回容器中的下一個值，任何實現了__iter__和__next__（python2中實現next()）方法的對象都是迭代器，__i ...
迭代器
可迭代對象:可迭代對象實現了__iter__方法，該方法返回一個迭代器對象。
迭代器: 那麼什麼迭代器呢？它是一個帶狀態的對象，他能在你調用next()方法的時候返回容器中的下一個值，任何實現了__iter__和__next__（python2中實現next()）方法的對象都是迭代器，__iter__返回迭代器自身，__next__返回容器中的下一個值，如果容器中沒有更多元素了，則拋出StopIteration異常。
a = ['aaa', 'bbb', 'ccc']
my_iterable = MyIterable(a)
res2 = iter(my_iterable)
while True:
try:
print(next(res2))
except StopIteration as e:
break生成器
class Project(object):
def __init__(self, start, end):
self.start = start
self.end = end
def isPrimeNum(self, k): # 判斷素數
if k < 2:
return False
for i in range(2, k):
if k % i == 0:
return False
return True
def __iter__(self):
for i in range(self.start, self.end):
if self.isPrimeNum(i):
yield i
###################################
res = Project(1,100)
print(iter(res))正反序的自定義生成器
class MyFloatRange(object):
def __init__(self, start, end, step):
self.start = start
self.end = end
self.step = step
def __iter__(self):
for i in range(self.start, self.end):
if self.start <= self.end:
yield self.start
self.start += self.step
def __reversed__(self):
for i in range(self.start, self.end):
if self.start <= self.end:
yield self.end
self.end -= self.step
for i in MyFloatRange(1, 11, 2):
print(i)
for i in reversed(MyFloatRange(1, 11, 2)):
print(i)如何對迭代器做切片操作
我們使用from itertools import islice
from itertools import islice
#對文件的每一行做切片操作
f = open("xxx.txt", "r")
res = islice(f, 3, 9)
迴圈res如何在for迴圈中迭代多個對象(並行)
我們通過zip這個拉鏈函數
from random import randint
chin = [randint(50, 100) for _ in range(40)]
math = [randint(50, 100) for _ in range(40)]
eigh = [randint(50, 100) for _ in range(40)]
for x,y,z in zip(chin, math, eigh):
print(x, y, z)如何在for迴圈中迭代多個對象(串列)
我們通過from itertools import chain函數
from random import randint
from itertools import chain
chin = [randint(50, 100) for _ in range(5)]
math = [randint(50, 100) for _ in range(5)]
eigh = [randint(50, 100) for _ in range(5)]
for i in chain(chin, math, eigh):
print(i)
