Python中yield表达式的结果是什么? [英] What is the result of a yield expression in Python?

问题描述

我知道yield将函数转换为生成器，但是yield表达式本身的返回值是多少?例如:

I know that yield turns a function into a generator, but what is the return value of the yield expression itself? For example:

def whizbang(): 
    for i in range(10): 
        x = yield i

该函数执行时变量x的值是什么?

What is the value of variable x as this function executes?

我已阅读Python文档: http://docs. python.org/reference/simple_stmts.html#grammar-token-yield_stmt ，似乎没有提及yield表达式本身的值.

I've read the Python documentation: http://docs.python.org/reference/simple_stmts.html#grammar-token-yield_stmt and there seems to be no mention of the value of the yield expression itself.

推荐答案

您还可以send值生成器.如果未发送任何值，则x为None，否则x接受发送的值.这里是一些信息: http://docs.python. org/whatsnew/2.5.html#pep-342-new-generator-features

You can also send values to generators. If no value is sent then x is None, otherwise x takes on the sent value. Here is some info: http://docs.python.org/whatsnew/2.5.html#pep-342-new-generator-features

>>> def whizbang():
        for i in range(10):
            x = yield i
            print 'got sent:', x


>>> i = whizbang()
>>> next(i)
0
>>> next(i)
got sent: None
1
>>> i.send("hi")
got sent: hi
2

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