擅长:python、mysql、java
<p>对于计数<code>True</code>的<a href="http://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.str.startswith.html" rel="nofollow noreferrer">^{<cd1>}</a>和<code>sum</code>的解决方案:</p>
<pre><code>print (pd.Series(df['something'].unique()).str.startswith('aa').sum())
3
</code></pre>
<p>备选方案是<a href="http://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.drop_duplicates.html" rel="nofollow noreferrer">^{<cd4>}</a>-那么<code>Series</code>构造函数是不必要的:</p>
<pre><code>print (df['something'].drop_duplicates().str.startswith('aa').sum())
3
</code></pre>
<p>或纯python解决方案生成器,带有<code>sum</code>和<code>startswith</code>用于计数<code>True</code>:</p>
<pre><code>print (sum(x.startswith('aa') for x in df['something'].unique()))
3
</code></pre>