Python迭代器和生成器定义与用法示例

li=[1,2,3,4,56,78]
a=iter(li)
print(a.__next__())
print(a.__next__())
print(a.__next__())
print(a.__next__())
print(a.__next__())
print(a.__next__()) #取值到最后一个元素787
print(a.__next__())

1
2
3
4
56
78
#开始报错
Traceback (most recent call last):
 File "/Users/shane/PycharmProjects/Py_study/Base/S5/iter_test.py", line 14, in <module>
  print(a.__next__())
StopIteration

def func():
  print(111)
  yield 1
  print(222)
  yield 2
  print(333)
  yield 3
ret=func()
r1=ret.__next__()
print(r1) #如果没有 print,只会返回111

111
1

def func():
  print(111)
  yield 1
  print(222)
  yield 2
  print(333)
  yield 3
ret=func()
r1=ret.__next__()
print(r1)
r2=ret.__next__()
print(r2)
r3=ret.__next__()
print(r3)
r4=ret.__next__()  #如果没有 r4就不会报错,因为已经没值可取了
print(r4)

Traceback (most recent call last):
 File "/Users/shane/PycharmProjects/Py_study/Base/S5/geno.py", line 21, in <module>
  r4=ret.__next__()
StopIteration
111
1
222
2
333
3

def myrange(args):
  start=0
  while True:
    if start > args:
      return
    else:
      yield start
      start+=1
res=myrange(3)
ret=res.__next__()
print(ret)
ret=res.__next__()
print(ret)
ret=res.__next__()
print(ret)
ret=res.__next__()
print(ret)
ret=res.__next__()
print(ret)