擅长:python、mysql、java
<p>你的问题是变量url可能永远不会被赋值。原因是你的if条件。在</p>
<pre><code>if condition1:
url = "something"
else:
if condition2:
url = "something"
elif condition3:
url = "something"
elif condition4:
url = "something"
else: # hypothetical
url is undefined here # and here is your issue
</code></pre>
<p>您可以通过添加最后一个else捕获或在检查任何条件之前将url初始化为默认值来解决此问题。在</p>
<p>如果您使用像<a href="https://www.jetbrains.com/pycharm/" rel="nofollow noreferrer">Pycharm</a>这样的好IDE,它甚至会在运行代码之前就警告您这些问题。在</p>