title: Concat multiple shapefiles via geopandas
body: <p>I'm trying to combine multiple shapefiles by implementing the follwing:</p>
  
  <pre><code>import geopandas as gpd
  import pandas as pd
  
  for i in range(10,56):
      interesting_files = "/Users/m3105/Downloads/area/tl_2015_{}_arealm.shp".format(i)
      gdf_list = []
      for filename in sorted(interesting_files):
          gdf_list.append(gpd.read_file((filename)))
          full_gdf = pd.concat(gdf_list)
  </code></pre>
  
  <p>in which the directory <code>/Users/m3105/Downloads/area</code> has several shapefiles with such as <code>tl_2015_01_arealm.shp</code>, <code>tl_2015_02_arealm.shp</code> all the way up to <code>tl_2015_56_arealm.shp</code>. I'd like to combine all of these shapefiles and avoid repeating their headers. However, whenever I try concating the files using the code above, I get the following error:</p>
  
  <p><code>ValueError: Null layer: u''</code></p>
  
  <p>Normally, I'd know how to concat csv files together but I'm note sure how to concat shapefiles. I'd greatly appreciate any help</p>