擅长:python、mysql、java
<p><code>pred=predecessors.get(pred,None)</code>相当于</p>
<pre><code>pred=predecessors[pred] if pred in predecessors else None
</code></pre>
<p>这和</p>
^{pr2}$
<p>同样,<code>if new_distance < distances.get(neighbor,float('inf')):</code>相当于</p>
^{3}$
<p>并且<code>unvisited[k] = distances.get(k,float('inf'))</code>相当于</p>
<pre><code>unvisited[k] = distances[k] if k in distances else float('inf')
</code></pre>