title: Insert string to Dataframe in python 3.6.0
body: <p>I want to find the folder path for all <code>.gz</code> files from network folder.
  I have below <code>script</code> but its giving <code>error</code>: </p>
  
  <pre><code>TypeError: cannot concatenate a non-NDFrame object
  </code></pre>
  
  <p>Please help on the same</p>
  
  <p>Script:</p>
  
  <pre><code>import os
  import pandas as pd
  
  adcPath = r'\\ADC\redshift-datasets\BLSCEWAG2016'
  
  gzPath = pd.DataFrame(columns=['Path'], dtype=object)
  for path, subdirs, files in os.walk(adcPath):
  for name in files:
  if name.endswith('.gz'):
  gzPath = gzPath.append(path) # Want to insert to dataframe gzPath to export in csv
  
  gzPath = gzPath['Path'].unique()
  exportPath = r'D:\Sunil_Work\temp8' + '\\Path.csv'
  gzPath.to_csv(exportPath)
  </code></pre>