title: Replacing a string completely with a new string or word in python
body: <p>I have a data frame which has two columns, "Title" and "Description". The title column has a bunch of titles related to clinical lab tests. Unfortunately, most of the titles are repeat of same test but  due to minor changes in the titles,  titles are shown as  unique. </p>
  
  <pre><code>values = [('Complete blood picture', 'AB'), ('Complete BLOOD test', 'AB'), ('blood glucose', 'AB'), ('COMplete blood Profile', 'AB')]
  labels = ['title', 'description']
  import pandas as pd
  labtest = pd.DataFrame.from_records(values, columns = labels) # Create data frame
  labtest = labtest.apply(lambda x: x.astype(str).str.lower())  # Convert columns to string and lower case
  labtest['title'].str.contains("blood")  # Search for blood
  </code></pre>
  
  <p>Before:</p>
  
  <pre><code>Title                       Description
  Complete blood test         AB
  COMPLETE Blood test\        AB
  Blood glucose               AB
  Complete blood picture      AB
  </code></pre>
  
  <p>After: [This is how i would like the data frame to look like]</p>
  
  <pre><code>Title                       Description
  Blood test                   AB
  Blood test                   AB
  Blood test                   AB
  Blood test                   AB
  </code></pre>
  
  <p>I would like to search for the word "blood" in each title and if its true, then change the whole title with "Blood test".</p>
  
  <p>P.S I am new to python and working with text data, i have only managed to come as far as search for the word "blood".</p>