title: Python how to create new dataset from an existing one based on condition
body: <p>For example:
  I have this code:</p>
  <pre><code>import pandas
  df = pandas.read_csv('covid_19_data.csv')
  </code></pre>
  <p>this dataset has a column called <code>countryterritoryCode</code> which is the country code of the country.<a href="https://i.stack.imgur.com/5hlCC.png" rel="nofollow noreferrer">sample data from the dataset</a></p>
  <p>This dataset has information about covid19 cases from all the countries in the world.
  How do I create a new dataset where only the USA info appears
  (where <code>countryterritoryCode == USA</code>)</p>