Pandas use variable for column names
<p>Given the following data frame:</p>

<pre><code>import pandas as pd
import numpy as np
df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6],
                   'C':[7,8,9]})

df

    A   B   C
0   1   4   7
1   2   5   8
2   3   6   9
</code></pre>

<p>How can I access columns via a variable?</p>

<p>I tried this:</p>

<pre><code>cols='A','B'
df[cols]
</code></pre>

<p>...which resulted in this:</p>

<pre><code>KeyError: ('A', 'B')
</code></pre>

<p>Bonus Question:
What if my data frame were like this?:</p>

<pre><code>import pandas as pd
import numpy as np
df = pd.DataFrame({'A':[1,2,3],
                   'B':[4,5,6],
                   'C':[7,8,9],
                   'D':[1,3,5],
                   'E':[5,3,6],
                   'F':[7,4,3]})

df

    A   B   C   D   E   F
0   1   4   7   1   5   7
1   2   5   8   3   3   4
2   3   6   9   5   6   3
</code></pre>

<p>and I wanted to do this?:</p>

<pre><code>cols=['A','B']
cols2=['C','D']
df[cols,'F',cols2]
</code></pre>

<p>Thanks in advance!</p>