擅长:python、mysql、java
<p><code>get()</code>返回<code>None</code>如果找不到该项,顺便说一句,您可以将第二个可选参数传递给<code>get()</code>。因此,如果没有找到<code>id</code>,那么返回该参数</p>
<pre><code>>>> dic={'2': '150.99', '3': '99.50', '15': '5.07'}
>>> items= ['2', '2', '3']
>>> sum(float(dic.get(x,0)) for x in items) #pass 0 to get in case id is not there
401.48
</code></pre>
<p><code>help(dict.get)</code>:</p>
<pre><code>get(...)
D.get(k[,d]) -> D[k] if k in D, else d. d defaults to None.
</code></pre>