擅长:python、mysql、java
<p>为什么不在模型中添加一个<em>gain()</em>方法呢?在</p>
<pre><code>class Purchase(models.Model):
ticker = models.CharField(max_length=5)
date = models.DateField()
price = models.DecimalField(max_digits=20, decimal_places=3)
quantity = models.IntegerField()
def gain(self, todays_price=None):
if not todays_price:
todays_price = get_price_from_webservice(self.ticker)
result_gain = todays_price - self.price
return result_gain
</code></pre>
<p>然后你就可以随心所欲了:</p>
^{pr2}$