擅长:python、mysql、java
<p>使用<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.where.html?highlight=where#pandas.DataFrame.where" rel="noreferrer">^{<cd1>}</a>的<code>other</code>参数和<a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.concat.html" rel="noreferrer">^{<cd3>}</a>:</p>
<pre><code>>>> import pandas as pd
>>>
>>> foo = pd.DataFrame([
... ['USA',1,2],
... ['Canada',3,4],
... ['Canada',5,6]
... ], columns=('Country', 'x', 'y'))
>>>
>>> z = foo['x'].where(foo['Country'] == 'USA', foo['y'])
>>> pd.concat([foo['Country'], z], axis=1)
Country x
0 USA 1
1 Canada 4
2 Canada 6
</code></pre>
<p>如果要将<code>z</code>作为列名,请指定<code>keys</code>:</p>
<pre><code>>>> pd.concat([foo['Country'], z], keys=['Country', 'z'], axis=1)
Country z
0 USA 1
1 Canada 4
2 Canada 6
</code></pre>