擅长:python、mysql、java
<p>您可以使用<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.map.html" rel="nofollow noreferrer">^{<cd1>}</a>+<a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.fillna.html" rel="nofollow noreferrer">^{<cd2>}</a></p>
<pre><code>df1['Code_1'] = df1['User_ID'].map(df2.set_index('User_ID')['Code_2'])\
.fillna(df1['Code_1'])
print(df1)
# User_ID Code_1
# 0 123 ert
# 1 345 nad
# 2 567 cewr
</code></pre>
<p>其思想是在执行映射时对齐索引,如果<code>df2</code>中不存在映射,则用原始值填充索引</p>