>>> gen = (x**2 for x in range(5))
>>> gen
<generator object <genexpr> at 0x0000000002FB7B40>
>>> for g in gen:
...  print(g, end='-')
...
0-1-4-9-16-
>>> for x in [0,1,2,3,4,5]:
...  print(x, end='-')
...
0-1-2-3-4-5-

def
odd():
n=1
while
True:
yield
n
n+=2
odd_num
=
odd()
count
=
0
for
o
in
odd_num:
if
count
>=5:
break
print(o)
count
+=1

class Iter:
  def __init__(self):
    self.start=-1
  def __iter__(self):
    return self
  def __next__(self):
    self.start +=2 
    return self.start
I = Iter()
for count in range(5):
  print(next(I))

>>>
from
collections
import
Iterable
>>>
from
collections
import
Iterator
>>>
isinstance(odd_num,
Iterable)
True
>>>
isinstance(odd_num,
Iterator)
True
>>>
iter(odd_num)
is
odd_num
True
>>>
help(odd_num)
Help
on
generator
object:
odd
=
class
generator(object)
| Methods
defined
here:
|
| __iter__(self,
/)
|   Implement
iter(self).
|
| __next__(self,
/)
|   Implement
next(self).
......

>>> def g1():
...   yield 1
...
>>> g=g1()
>>> next(g)  #第一次調(diào)用next(g)時(shí)，會(huì)在執(zhí)行完yield語句后掛起，所以此時(shí)程序并沒有執(zhí)行結(jié)束。
1
>>> next(g)  #程序試圖從yield語句的下一條語句開始執(zhí)行，發(fā)現(xiàn)已經(jīng)到了結(jié)尾，所以拋出StopIteration異常。
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration
>>>

>>>
def
g2():
...  
yield
'a'
...  
return
...  
yield
'b'
...
>>>
g=g2()
>>>
next(g)  #程序停留在執(zhí)行完yield
 'a'語句后的位置。
'a'
>>>
next(g)  #程序發(fā)現(xiàn)下一條語句是return，所以拋出StopIteration異常，這樣yield
 'b'語句永遠(yuǎn)也不會(huì)執(zhí)行。
Traceback
(most
recent
call
last):
 File
"<stdin>",
line
1,
in
<module>
StopIteration

>>> def g3():
...   yield 'hello'
...   return 'world'
...
>>> g=g3()
>>> next(g)
'hello'
>>> next(g)
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration: world

>>>
help(odd_num)
Help
on
generator
object:
odd
=
class
generator(object)
| Methods
defined
here:
......
| close(...)
|   close()
->
raise
GeneratorExit
inside
generator.
|
| send(...)
|   send(arg)
->
send
'arg'
into
generator,
|   return
next
yielded
value
or
raise
StopIteration.
|
| throw(...)
|   throw(typ[,val[,tb]])
->
raise
exception
in
generator,
|   return
next
yielded
value
or
raise
StopIteration.
......

>>> def g4():
...   yield 1
...   yield 2
...   yield 3
...
>>> g=g4()
>>> next(g)
1
>>> g.close()
>>> next(g)  #關(guān)閉后，yield 2和yield 3語句將不再起作用
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteration

def
gen():
  value=0
  while
True:
    receive=yield
value
    if
receive=='e':
      break
    value
=
'got: %s'
%
receive
g=gen()
print(g.send(None)) 
print(g.send('aaa'))
print(g.send(3))
print(g.send('e'))

0
got: aaa
got: 3
Traceback (most recent call last):
File "h.py", line 14, in <module>
 print(g.send('e'))
StopIteration

def
gen():
  while
True:
    try:
      yield
'normal value'
      yield
'normal value 2'
      print('here')
    except
ValueError:
      print('we
 got ValueError here')
    except
TypeError:
      break
g=gen()
print(next(g))
print(g.throw(ValueError))
print(next(g))
print(g.throw(TypeError))

normal value
we got ValueError here
normal value
normal value 2
Traceback (most recent call last):
 File "h.py", line 15, in <module>
  print(g.throw(TypeError))
StopIteration

def
flatten(nested):
  try:
    #如果是字符串，那么手動(dòng)拋出TypeError。
    if
isinstance(nested,
str):
      raise
TypeError
    for
sublist
in
nested:
      #yield
 flatten(sublist)
      for
element
in
flatten(sublist):
        #yield
 element
        print('got:',
element)
  except
TypeError:
    #print('here')
    yield
nested
L=['aaadf',[1,2,3],2,4,[5,[6,[8,[9]],'ddf'],7]]
for
num
in
flatten(L):
  print(num)