title: 'str' object has no attribute 'str'
body: <p>I am trying to print the columns that contain tu anywhere in the title.
  According to <a href="https://pandas.pydata.org/pandas-docs/stable/api.html#string-handling" rel="nofollow noreferrer">String Documentation</a> this should work, but I get an error</p>
  
  <blockquote>
    <p>'str' object has no attribute 'str'</p>
  </blockquote>
  
  <p>I am trying to have have a dataframe with the columns containing tu only</p>
  
  <pre><code>import numpy as np
  import pandas as pd
  from sklearn.datasets import make_classification
  
  X, y = make_classification(n_samples=1000,
                             n_features=6,
                             n_informative=3,
                             n_classes=2,
                             random_state=0,
                             scale = 10,
                             shuffle=False)
  
  # Creating a dataFrame
  df = pd.DataFrame({'car':X[:,0],
                                    'ball':X[:,1],
                                    'Feature 3': 5,
                                    'Feature 4':X[:,3],
                                    'Feature 5':X[:,4],
                                    'Feature 6':X[:,5],
                                    'Class':y})
  
  
  spike_cols = [col for col in df.columns if col.str.contains("tu")]
  print(spike_cols)
  </code></pre>