11.10 生成器:

与迭代器相似,生成器以另外的方式来运作:当到达一个真正的返回或者函数结束没有更多的值返回(

当调用next(),一个 StopIteration异常就会抛出

def simpleGen():
    yield 1
    yield '2-->'
    yield 3
a=simpleGen()
print a
print type(a)

C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/eee/a9.py
<generator object simpleGen at 0x0208BDF0>
<type 'generator'>

Process finished with exit code 0


def simpleGen():
    yield 1
    yield '2-->'
    yield 3
a=simpleGen()
print a
print type(a)

print a.next()
print a.next()
print a.next()
print a.next()

C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/eee/a9.py
<generator object simpleGen at 0x0236F4E0>
<type 'generator'>
1
2-->
3
Traceback (most recent call last):
  File "C:/Users/TLCB/PycharmProjects/untitled/mycompany/eee/a9.py", line 12, in <module>
    print a.next()
StopIteration


由于python 的for 循环有next()调用和对StopIteration的处理,使用一个for 循环而不是手动迭代穿过一个生成器

def simpleGen():
    yield 1
    yield '2-->'
    yield 3
a=simpleGen()
print a
print type(a)

for eachItem in simpleGen():
    print eachItem
	
	
from random import randint
def randGen(aList):
    while len(aList) > 0:
        yield aList.pop()
a=randGen([1,2,3,4,0])
print a.next()
print a.next()
print a.next()
print a.next()

C:\Python27\python.exe C:/Users/TLCB/PycharmProjects/untitled/mycompany/eee/a9.py
0
4
3
2