由浅入深讲解python中的yield与generator

def gen_generator():
 yield 1

def gen_value():
 return 1
 
if __name__ == '__main__':
 ret = gen_generator()
 print ret, type(ret) #<generator object gen_generator at 0x02645648> <type 'generator'>
 ret = gen_value()
 print ret, type(ret) # 1 <type 'int'>

>>> def gen_example():
... print 'before any yield'
... yield 'first yield'
... print 'between yields'
... yield 'second yield'
... print 'no yield anymore'
... 
>>> gen = gen_example()
>>> gen.next()　　　　＃ 第一次调用next
before any yield
'first yield'
>>> gen.next()　　　　＃ 第二次调用next
between yields
'second yield'
>>> gen.next()　　　　＃ 第三次调用next
no yield anymore
Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
StopIteratio

def generator_example():
 yield 1
 yield 2

if __name__ == '__main__':
 for e in generator_example():
 print e
 # output 1 2

　　>>> gen = (x * x for x in xrange(5))
　　>>> print gen
　　<generator object <genexpr> at 0x02655710>

RANGE_NUM = 100
 for i in [x*x for x in range(RANGE_NUM)]: # 第一种方法：对列表进行迭代
 # do sth for example
 print i

 for i in (x*x for x in range(RANGE_NUM)): # 第二种方法：对generator进行迭代
 # do sth for example
 print i

def fib():
 a, b = 1, 1
 while True:
 yield a
 a, b = b, a+b 

def gen_data_from_file(file_name):
 for line in file(file_name):
 yield line

def gen_words(line):
 for word in (w for w in line.split() if w.strip()):
 yield word

def count_words(file_name):
 word_map = {}
 for line in gen_data_from_file(file_name):
 for word in gen_words(line):
  if word not in word_map:
  word_map[word] = 0
  word_map[word] += 1
 return word_map

def count_total_chars(file_name):
 total = 0
 for line in gen_data_from_file(file_name):
 total += len(line)
 return total
 
if __name__ == '__main__':
 print count_words('test.txt'), count_total_chars('test.txt')

 def do(a):
 print 'do', a
 CallBackMgr.callback(5, lambda a = a: post_do(a))
 
 def post_do(a):
 print 'post_do', a

 @yield_dec
 def do(a):
 print 'do', a
 yield 5
 print 'post_do', a

# -*- coding:utf-8 -*-
import sys
# import Timer
import types
import time

class YieldManager(object):
 def __init__(self, tick_delta = 0.01):
 self.generator_dict = {}
 # self._tick_timer = Timer.addRepeatTimer(tick_delta, lambda: self.tick())

 def tick(self):
 cur = time.time()
 for gene, t in self.generator_dict.items():
  if cur >= t:
  self._do_resume_genetator(gene,cur)

 def _do_resume_genetator(self,gene, cur ):
 try:
  self.on_generator_excute(gene, cur)
 except StopIteration,e:
  self.remove_generator(gene)
 except Exception, e:
  print 'unexcepet error', type(e)
  self.remove_generator(gene)

 def add_generator(self, gen, deadline):
 self.generator_dict[gen] = deadline

 def remove_generator(self, gene):
 del self.generator_dict[gene]

 def on_generator_excute(self, gen, cur_time = None):
 t = gen.next()
 cur_time = cur_time or time.time()
 self.add_generator(gen, t + cur_time)

g_yield_mgr = YieldManager()

def yield_dec(func):
 def _inner_func(*args, **kwargs):
 gen = func(*args, **kwargs)
 if type(gen) is types.GeneratorType:
  g_yield_mgr.on_generator_excute(gen)

 return gen
 return _inner_func

@yield_dec
def do(a):
 print 'do', a
 yield 2.5
 print 'post_do', a
 yield 3
 print 'post_do again', a

if __name__ == '__main__':
 do(1)
 for i in range(1, 10):
 print 'simulate a timer, %s seconds passed' % i
 time.sleep(1)
 g_yield_mgr.tick()

def visit(data):
 for elem in data:
 if isinstance(elem, tuple) or isinstance(elem, list):
  visit(elem) # here value retuened is generator
 else:
  yield elem
  
if __name__ == '__main__':
 for e in visit([1, 2, (3, 4), 5]):
 print e

def visit(data):
 for elem in data:
 if isinstance(elem, tuple) or isinstance(elem, list):
  for e in visit(elem):
  yield e
 else:
  yield elem

 def visit(data):
 for elem in data:
  if isinstance(elem, tuple) or isinstance(elem, list):
  yield from visit(elem)
  else:
  yield elem

def gen_with_return(range_num):
 if range_num < 0:
 return
 else:
 for i in xrange(range_num):
  yield i

if __name__ == '__main__':
 print list(gen_with_return(-1))
 print list(gen_with_return(1))

 def gen_with_return(range_num):
 if range_num < 0:
  return 0
 else:
  for i in xrange(range_num):
  yield i