擅长:python、mysql、java
<p>您可以使用<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.mask.html" rel="noreferrer">^{<cd1>}</a>:</p>
<pre><code>mask = df['value'] < 0
df['main_val'] = df['value'].mask(mask)
df['sub_val'] = df['value'].mask(~mask)
df = df.drop(['col1','col2', 'value'], axis=1)
print (df)
time main_val sub_val
0 16:00:00 100.0 NaN
1 17:00:00 NaN -40.0
2 18:00:45 300.0 NaN
3 20:04:33 NaN -89.0
</code></pre>