擅长:python、mysql、java
<p>下面应该可以做到这一点:</p>
<pre><code>import numpy as np
mask = df.Total_dll < 1.
df.loc[mask, 'Total_dll'] = np.nan
</code></pre>
<hr/>
<p>如果<code>Total_dll</code>属于<code>string</code>类型,您可以尝试以下操作:</p>
<pre><code>import numpy as np
df.str.startswith('<')
df.loc[df.Total_dll.str.startswith('<'), np.nan]
</code></pre>