擅长:python、mysql、java
<p>你可以在这里使用<a href="https://docs.scipy.org/doc/numpy/reference/generated/numpy.select.html" rel="nofollow noreferrer">^{<cd1>}</a></p>
<pre><code>m = df2['Marks1'].notna()
m1 = df2['Marks1'].isna() & df2['Marks2'].notna()
condlist = [m,m1]
choice = [df2['Marks1'] , df2['Marks2']]
df1['Total'] = np.select(condlist,choice,np.nan)
No Total
0 1234 99.0
1 2515 98.0
2 3412 20.0
3 4854 98.0
4 7732 NaN
</code></pre>