擅长:python、mysql、java
<p>您需要为<code>fields</code>使用元组或列表,要用单个项表示元组,您需要使用尾随逗号:</p>
<pre><code>fields = ('test', )
</code></pre>
<p>没有逗号<code>fields = ('test')</code>实际上相当于<code>fields = 'test'</code>。在</p>
<p>来自<a href="http://docs.python.org/2/tutorial/datastructures.html#tuples-and-sequences">docs</a>:</p>
<blockquote>
<p>A special problem is the construction of tuples containing 0 or 1
items: the syntax has some extra quirks to accommodate these. Empty
tuples are constructed by an empty pair of parentheses; a tuple with
one item is constructed by following a value with a comma (it is not
sufficient to enclose a single value in parentheses). Ugly, but
effective.</p>
</blockquote>