title: Pandas Dataframe How to cut off float decimal points without rounding?
body: <p>I have longitude and latitude in two dataframes that are close together. If I run an exact similarity check such as</p>
  
  <pre class="lang-py prettyprint-override"><code>test_similar = test1_latlon.loc[~test1_latlon['cr'].isin(test2_latlon['cr'])]
  </code></pre>
  
  <p>I get a lot of failures because a lot of the numbers are off at the 5th decimal place. I want to truncate at after the 3rd decimal. I've seen people format so it shows up truncated, but I want to change the actual value. Using <code>round()</code> rounds off the data and I get even more errors, so is there a way to just drop after 3 decimal points? </p>