title: Pandas group by one column concatenate values of other column as delimited list
body: <p>I want to group all qualifications(as a delimiter separated list) against a job title. </p>
  
  <p>In the following dataset, same type of job (.net developer) require different set of qualifications and another job does not require any qualification. </p>
  
  <pre><code>JobID    Job Title      Qualification ID Qualification Name
  34455226 .Net Developer ICT50715         Diploma of Software Development
  34455226 .Net Developer ICT40515         Certificate IV in Programming
  34466933 .Net Developer ICT50715         Diploma of Software Development
  34466111 .Net Developer ICT50655         Diploma of Software Testing
  34479964 Snr Finance Systems Analyst 
  </code></pre>
  
  <p>I want a consolidated view of all unique qualifications that might be required for a particular type of job as below</p>
  
  <pre><code>Job Title                     Qualifications
  .Net Developer                Diploma of Software Development,Certificate IV in Programming,Diploma of Software Testing
  Snr Finance Systems Analyst   N/A
  </code></pre>
  
  <p>This is what I have done so far.</p>
  
  <pre><code>def f(x):
   return pd.Series(dict(Qualifications = ",".join(map(str, x["Qualification Name"]))))
  
  df_jobs_qualifications\
      .groupby("Job Title")[['Qualification Name']]\
      .apply(f)
  </code></pre>
  
  <p>But it gives me repeated qualification names (see below - Diploma of Software Development is repeated) whereas I want unique qualification names </p>
  
  <pre><code>Job Title                     Qualifications
  .Net Developer                Diploma of Software Development,Certificate IV in Programming,Diploma of Software Development,Diploma of Software Testing
  Snr Finance Systems Analyst   N/A
  </code></pre>
  
  <p><strong>UPDATE</strong></p>
  
  <p>My question is different from <a href="https://stackoverflow.com/questions/44368537/pandas-groupby-with-delimiter-join">this</a> question as in I do not get unique values even after following the steps mentioned on the before mentioned question
  <a href="https://i.stack.imgur.com/SAO1E.png" rel="noreferrer"><img src="https://i.stack.imgur.com/SAO1E.png" alt="enter image description here"></a></p>