Pandas: IndexingError: Unalignable boolean Series provided as indexer : <p>I'm trying to run what I think is simple code to eliminate any columns with all NaNs, but can't get this to work (<code>axis = 1</code> works just fine when eliminating rows):</p>

<pre><code>import pandas as pd
import numpy as np

df = pd.DataFrame({'a':[1,2,np.nan,np.nan], 'b':[4,np.nan,6,np.nan], 'c':[np.nan, 8,9,np.nan], 'd':[np.nan,np.nan,np.nan,np.nan]})

df = df[df.notnull().any(axis = 0)]

print df
</code></pre>

<p>Full error:</p>

<p><code>raise IndexingError('Unalignable boolean Series provided as 'pandas.core.indexing.IndexingError: Unalignable boolean Series provided as indexer (index of the boolean Series and of the indexed object do not match</code></p>

<p>Expected output:</p>

<pre><code>     a    b    c
0  1.0  4.0  NaN
1  2.0  NaN  8.0
2  NaN  6.0  9.0
3  NaN  NaN  NaN
</code></pre>
