title: Pandas how to place an array in a single dataframe cell?
body: <p>So I currently have a dataframe that looks like:</p>
  
  <p><img src="https://i.stack.imgur.com/QW7hp.png" alt="Current Dataframe"></p>
  
  <p>And I want to add a completely new column called "Predictors" with only one cell that contains an array.  </p>
  
  <p>So [0, 'Predictors'] should contain an array and everything below that cell in the same column should be empty.</p>
  
  <p>Here's my attempt, I tried to create a separate dataframe that just contained the "Predictors" column, and tried appending it to the current dataframe, but I get: 'Length mismatch: Expected axis has 3 elements, new values have 4 elements.'</p>
  
  <p>How do I append a single cell containing an array to my dataframe?</p>
  
  <pre><code># create a list and dataframe to hold the names of predictors
  dataframe=dataframe.drop(['price','Date'],axis=1)  
  predictorsList = dataframe.columns.get_values().tolist()
  predictorsList = np.array(predictorsList, dtype=object)
  
  # Combine actual and forecasted lists to one dataframe
  combinedResults = pd.DataFrame({'Actual': actual, 'Forecasted': forecasted})
  
  predictorsDF = pd.DataFrame({'Predictors': [predictorsList]})
  
  # Add Predictors to dataframe
  #combinedResults.at[0, 'Predictors'] = predictorsList
  pd.concat([combinedResults,predictorsDF], ignore_index=True, axis=1)
  </code></pre>