将本地变量添加到运行的生成器

Question

最近,我尝试从正在运行的生成器外部设置局部变量.生成器代码也应该访问这些变量.

一个问题是,当访问变量时,它会解释为解释器认为它必须是全局的,因为变量未在本地范围中设置.但我不想改变全局变量,也不想复制整个全局范围以使变量人为地局部化.

另一个麻烦是,当从外部访问时,它本地(以及全局变量？)的字典接合为只读.

是否有任何合法(或至少部分合法的方式)将本地人引入正在运行的生成器实例？

编辑以澄清:

我不是指"发送"功能.这当然是一个简洁的功能,但由于我想设置多个具有不同名称的变量,因此对我的目的而言并不方便.

Answer 1

您可能正在寻找的是send方法,它允许将值发送到生成器.该参考提供了一个例子:

>>> def echo(value=None):
...     print "Execution starts when 'next()' is called for the first time."
...     try:
...         while True:
...             try:
...                 value = (yield value)
...             except Exception, e:
...                 value = e
...     finally:
...         print "Don't forget to clean up when 'close()' is called."
...
>>> generator = echo(1)
>>> print generator.next()
Execution starts when 'next()' is called for the first time.
1
>>> print generator.next()
None
>>> print generator.send(2)
2
>>> generator.throw(TypeError, "spam")
TypeError('spam',)
>>> generator.close()
Don't forget to clean up when 'close()' is called.

让我举一个我自己的例子.(注意!上面的代码是Python 2.6,但下面我将编写Python 3; py3k ref):

>>> def amplify(iter, amp=1):
...     for i in iter:
...         reply = (yield i * amp)
...         amp = reply if reply != None else amp 
... 
>>> it = amplify(range(10))
>>> next(it)
0
>>> next(it)
1
>>> it.send(3) # 2 * 3 = 6
6
>>> it.send(8) # 3 * 8 = 24
24
>>> next(it) # 4 * 8 = 32
32

当然,如果你真的想要,你也可以不用这样做send.例如,通过将生成器封装在一个类中(但它不是那么优雅!):

>>> class MyIter:
...     def __init__(self, iter, amp=1):
...         self.iter = iter
...         self.amp = amp
...     def __iter__(self):
...         for i in self.iter:
...             yield i * self.amp
...     def __call__(self):
...         return iter(self)
... 
>>> iterable = MyIter(range(10))
>>> iterator = iterable()
>>> next(iterator)
0
>>> next(iterator)
1
>>> iterable.amp = 3
>>> next(iterator)
6
>>> iterable.amp = 8
>>> next(iterator)
24
>>> next(iterator)
32

更新:好的,既然你已经更新了你的问题,让我再次尝试解决这个问题.也许这就是你的意思？

>>> def amplify(iter, loc={}):
...     for i in iter:
...         yield i * loc.get('amp', 1)
... 
>>> it = amplify(range(10), locals())
>>> next(it)
0
>>> next(it)
1
>>> amp = 3
>>> next(it)
6
>>> amp = 8
>>> next(it)
24
>>> next(it)
32

请注意,locals()应将其视为只读且与范围相关.如您所见,您需要明确传递locals()给生成器.我看不到这个...