Feature #31: better error handling

Add dedicated exception and exit on specific error code.
Also put resource loading in separated functions.

colout/colout.py

@@ -128,31 +128,47 @@ def rgb_rainbow( x, freq = 1.0/(256.0/math.pi) ):
     return ( red, green, blue )
 
 
+class UnknownColor(Exception):
+    pass
+
+class DuplicatedPalette(Exception):
+    pass
+
+
 ###############################################################################
-# Load available extern ressources
+# Load available extern resources
 ###############################################################################
 
-# load available themes
+def load_themes( themes_dir):
+    global themes
     themes = {}
-themes_dir=os.path.dirname(os.path.realpath(__file__))
     os.chdir( themes_dir )
 
+    # load available themes
     for f in glob.iglob("colout_*.py"):
         module = ".".join(f.split(".")[:-1]) # remove extension
         name = "_".join(module.split("_")[1:]) # remove the prefix
         themes[name] = importlib.import_module(module)
 
-# load available colormaps (GIMP palettes format)
+
+def load_palettes( palettes_dir ):
+    global colormaps
     colormaps = {}
+    os.chdir( palettes_dir )
+
+    # load available colormaps (GIMP palettes format)
     for p in glob.iglob("*.gpl"):
         name,palette = parse_gimp_palette(p)
         if name in colormaps:
-        raise Exception('Duplicated palette filename: %s' % name)
+            raise DuplicatedPalette(name)
         # Convert the palette to ANSI
         ansi_palette = [ rgb_to_ansi(r,g,b) for r,g,b in palette ]
         # Compress it so that there isn't two consecutive identical colors
         colormaps[name] = uniq( ansi_palette )
 
+
+def load_lexers():
+    global lexers
     # load available pygments lexers
     lexers = []
     try:
@@ -172,6 +188,12 @@ else:
         lexers.sort()
 
 
+def load_resources( themes_dir, palettes_dir ):
+    load_themes( themes_dir )
+    load_palettes( palettes_dir )
+    load_lexers()
+
+
 ###############################################################################
 # Library
 ###############################################################################
@@ -316,7 +338,7 @@ def colorin(text, color="red", style="normal"):
 
     # unrecognized
     else:
-        raise Exception('Unrecognized color %s' % color)
+        raise UnknownColor(color)
 
     return start + style_code + endmarks[mode] + color_code + "m" + text + stop
 
@@ -595,6 +617,19 @@ def write_all( as_all, stream_in, stream_out, function, *args ):
 
 
 if __name__ == "__main__":
+    error_codes = {"UnknownColor":1, "DuplicatedPalette":2}
+
+    try:
+        # Search for available resources files (themes, palettes)
+        # in the same dir as the colout.py script
+        res_dir = os.path.dirname(os.path.realpath(__file__))
+
+        # this must be called before args parsing, because the help can list available resources
+        load_resources( res_dir, res_dir )
+
+    except DuplicatedPalette as e:
+        print( "ERROR in colout, duplicated palette file name: %s" % e )
+        sys.exit( error_codes["DuplicatedPalette"] )
 
     usage = "A regular expression based formatter that color up an arbitrary text stream."
 
@@ -611,6 +646,7 @@ if __name__ == "__main__":
         pattern, color, style, on_groups, as_colormap, as_theme, as_source, as_all, myscale \
             = __args_parse__(sys.argv, usage)
 
+    try:
         if myscale:
             scale = map(int,myscale.split(","))
 
@@ -644,3 +680,7 @@ if __name__ == "__main__":
         else:
             write_all( as_all, sys.stdin, sys.stdout, colorup, pattern, color, style, on_groups )
 
+    except UnknownColor as e:
+        print("ERROR in colout, unknown color: %s" % e )
+        sys.exit( error_codes["UnknownColor"] )
+