python 的 yield

以前只是类似生成器表达式那样使用... 其实有N多牛B用法. 真长见识~! http://www.dabeaz.com/coroutines/index.html 例如:

# grep.py
#
# A very simple coroutine

def grep(pattern):
  print "Looking for %s" % pattern
  while True:
    line = (yield)
    if pattern in line:
         print line,
# Example use
if __name__ == '__main__':
  g = grep("python")
  g.next()
  g.send("Yeah, but no, but yeah, but no")
  g.send("A series of tubes")
  g.send("python generators rock!")

对于生成器函数来说, 有 next() ,send(), throw() 方法.

• next() 比较容易理解.
• send(arg) 向生成器发送参数, 会被 line = (yield) 捕获.
• throw(typ[,val[,tb]]) -> raise exception in generator, return next yielded value or raise StopIteration. 参数分别是, 异常类型, 异常 str, traceback object.

这算是最简单的.... 配合函数修饰符, 相当强大.... yield ...