擅长:python、mysql、java
<p>这样做:</p>
<pre><code>table = {"username": {"inventory": {"apple": 2}}}
if (str(product)) in table["username"]["inventory"]:
table["username"]["inventory"][str(product)] += quantity
else:
table["username"]["inverntory"][str(product)] = quantity
</code></pre>
<p>要向现有字典添加新的键值对,您需要替换整个字典,而不是简单地执行<code>existing_dic[new_item] = value</code></p>