pandas DataFrame, how to apply function to a specific column? : <p>I have read the docs of <a href="http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.apply.html" rel="noreferrer">DataFrame.apply</a></p>

<blockquote>
  <p>DataFrame.apply(func, axis=0, broadcast=False, raw=False, reduce=None, args=(), **kwds)¶
  Applies function along input axis of DataFrame.</p>
</blockquote>

<p>So, How can I apply a function to a specific column?</p>

<pre><code>In [1]: import pandas as pd
In [2]: data = {'A': [1, 2, 3], 'B': [4, 5, 6], 'C': [7, 8, 9]}
In [3]: df = pd.DataFrame(data)
In [4]: df
Out[4]: 
   A  B  C
0  1  4  7
1  2  5  8
2  3  6  9
In [5]: def addOne(v):
...:        v += 1
...:        return v
...: 
In [6]: df.apply(addOne, axis=1)
Out[6]: 
   A  B   C
0  2  5   8
1  3  6   9
2  4  7  10
</code></pre>

<p>I want to addOne to every value in <code>df['A']</code>, not all columns. How can I do that with <code>DataFrame.apply</code>.</p>

<p>Thanks for help!  </p>
