擅长:python、mysql、java
<p>您可能要替换此:</p>
<pre><code>if set_date is not None:
</code></pre>
<p>有了这个:</p>
<pre><code>if set_date:
</code></pre>
<p>看看Python是如何计算if条件的:
<a href="https://docs.python.org/3/library/stdtypes.html" rel="nofollow noreferrer">Truth Value Testing (pydocs)</a></p>
<blockquote>
<p>Here are most of the built-in objects considered false:
constants defined to be false: None and False.
zero of any numeric type: 0, 0.0, 0j, Decimal(0), Fraction(0, 1)
empty sequences and collections: '', (), [], {}, set(), range(0)</p>
</blockquote>
<p>另外,“is”会给出一些奇怪的结果,它实际上是用来确定两个标签是否引用同一个对象的。
<a href="https://stackoverflow.com/questions/13650293/understanding-pythons-is-operator">Understanding Python's is operator</a></p>