Python: which is a fast way to find index in pandas dataframe?
<p>I have a dataframe like the following</p>

<pre><code>df = 
    a   ID1         ID2         Proximity
0   0   900000498   NaN         0.000000
1   1   900000498   900004585   3.900000
2   2   900000498   900005562   3.900000
3   3   900000498   900008613   0.000000
4   4   900000498   900012333   0.000000
5   5   900000498   900019524   3.900000
6   6   900000498   900019877   0.000000
7   7   900000498   900020141   3.900000
8   8   900000498   900022133   3.900000
9   9   900000498   900022919   0.000000
</code></pre>

<p>I want to find for a given couple <code>ID1-ID2</code> the corresponding <code>Proximity</code> value.
For instance given the input <code>[900000498, 900022133]</code> I want as output <code>3.900000</code></p>