title: Pandas: What is the difference between isin() and str.contains()?
body: <p>I want to know <strong>if a specific string is present in some columns of my dataframe</strong> (a different string for each column).
  From what I understand <a href="https://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.isin.html" rel="nofollow noreferrer"><code>isin()</code></a> is written for dataframes but can work for Series as well, while <a href="https://pandas.pydata.org/pandas-docs/version/0.23/generated/pandas.Series.str.contains.html" rel="nofollow noreferrer"><code>str.contains()</code></a> works better for Series.</p>
  <p>I don't understand how I should choose between the two. (I searched for similar questions but didn't find any explanation on how to choose between the two.)</p>