ValueError: Series lengths must match to compare when matching dates in Pandas : <p>I apologize in advance for asking such a basic question but I am stumped.</p>

<p>This is a very simple, dummy example. I'm having some issue matching dates in Pandas and I can't figure out why.</p>

<pre><code>df = pd.DataFrame([[1,'2016-01-01'], 
                   [2,'2016-01-01'],
                   [3,'2016-01-02'],
                   [4,'2016-01-03']],
                   columns=['ID', 'Date'])

df['Date'] = df['Date'].astype('datetime64')
</code></pre>

<p>Say I want to match row 1 in the above df.<br>
I know beforehand that I want to match ID <code>1</code>.<br>
And I know the date I want as well, and as a matter of fact, I'll extract that date directly from row 1 of the df to make it bulletproof.</p>

<pre><code>some_id = 1
some_date = df.iloc[1:2]['Date']  # gives 2016-01-01
</code></pre>

<p>So why doesn't this line work to return me row 1??</p>

<pre><code>df[(df['ID']==some_id) &amp; (df['Date'] == some_date)] 
</code></pre>

<p>Instead I get 
<code>ValueError: Series lengths must match to compare</code><br>
which I understand, and makes sense...but leaves me wondering...how else can I compare dates in pandas if I can't compare one to many?</p>
