擅长:python、mysql、java
<p>我们可以做条件<code>replace</code></p>
<pre><code>df['newcolumns']=df.col1.replace({'wrongstring':np.nan}).fillna(df.col2).fillna('newstring')
df
col1 col2 newcolumns
0 wrongstring correct correct
1 correctstring correct correctstring
2 correctstring correct correctstring
3 NaN correct correct
4 NaN NaN newstring
</code></pre>