擅长:python、mysql、java
<p>该语法用于属性,而不是键。如果要打印字典中的元素,请使用:</p>
<pre><code>print("Weight in tons {0[weight]}".format({'weight':10}))
</code></pre>
<p>以下是<code>.</code>语法的有效用法:</p>
<pre><code>class Dummy:
def __init__(self):
self.weight = 10
d = Dummy()
print("Weight in tons {0.weight}".format(d))
</code></pre>
<p>最后,不是这样:</p>
<pre><code>"Weight in tons {0.weight}".format({'weight':10})
</code></pre>
<p>…您可能打算使用命名参数语法:</p>
<pre><code>print("Weight in tons {weight}".format(weight=10))
</code></pre>