Tidy up argument parsing

scripts/dxf_to_csv.py

@@ -31,8 +31,7 @@ def point_to_row(point, layer, dxf_type, dxf_id):
     return row
 
 
-def convert(dxf_name, layer_name):
-    # Read dxf file
+def print_layers(dxf_name):
     dxf = dxfgrabber.readfile(dxf_name)
 
     # Get data from DTM
@@ -41,6 +40,11 @@ def convert(dxf_name, layer_name):
     for layer in layers:
         print(layer)
 
+
+def convert(dxf_name, layer_name):
+    # Read dxf file
+    dxf = dxfgrabber.readfile(dxf_name)
+
     if layer_name:
         print("\nExtracting data from layer '{}'".format(layer_name))
         entities = [
@@ -86,13 +90,26 @@ def convert(dxf_name, layer_name):
 
 
 def main():
-    dxf_name = sys.argv[1]
-    try:
-        layer_name = sys.argv[2]
-    except IndexError:
-        layer_name = None
-
-    convert(dxf_name, layer_name)
+    # Set up command line arguments
+    parser = argparse.ArgumentParser()
+    parser.add_argument('dxf_name', help='path to dxf file', default=None)
+    parser.add_argument(
+        '-n', metavar='LAYER_NAME', help='name of layer', default=None)
+    parser.add_argument(
+        '-l', action='store_true', help='show list of layers', default=False)
+    args = parser.parse_args()
+
+    # Parse arguments
+    dxf_name = args.dxf_name
+    layer_name = args.n
+    show_layers_only = args.l
+
+    if show_layers_only:
+        # Print list of layers only
+        print_layers(dxf_name)
+    else:
+        # Convert to csv
+        convert(dxf_name, layer_name)
 
 
 if __name__ == '__main__':