Pandas Mixed Type to Integer
<p>Given the following data frame:</p>

<pre><code>import pandas as pd
df = pd.DataFrame(
        {'A':['A','B','C','D'],
         'C':['1','12','*','8']
        })
df

    A   C
0   A   1
1   B   12
2   C   *
3   D   8
</code></pre>

<p>I'd like to remove all instances of '*' and convert the rest to integer.
There may be some instances of 'nan' or 'NaN' in my actual data.</p>