<p>因为循环中有3个yield语句,所以产生了<code>alpha</code>三次。在</p>
<p>因此:</p>
<ol>
<li>循环将迭代3个元素</li>
<li>对于每一个元素,你将得到3次</li>
</ol>
<p>3乘以3等于9。在</p>
<p>您的输出说明:</p>
<pre><code>1 < counter
('alpha', 'one') < first yield statement
2 < counter
('alpha', 'two') < second yield statement
3 < counter
('alpha', 'three') < third yield statement
< print statement in loop in function
4 < counter
('beta', 'one') < first yield statement, second iteration of loop
5 < counter
('beta', 'two') < second yield statement
6 < counter
('beta', 'three') < third yield statement
< print statement in loop in function
7 < counter
('carotene', 'one') < first yield statement, third iteration of loop
8 < counter
('carotene', 'two') < second yield statement
9 < counter
('carotene', 'three') < third yield statement
< print statement in loop in function
</code></pre>