Enhanced docstrings, commented an unclear bit of my contribution.

slideslurp/__init__.py

@@ -8,7 +8,10 @@ import requests
 import reportlab.pdfgen.canvas
 
 def parse_args():
-    """ Parse the command-line arguments. """
+    """ Parse the command-line arguments and return them as an object.
+    The returned object has the following properties:
+    - `url` (string): the URL of the slideshare to download;
+    - `out` (string): the output file path. """
     descr = "Generate PDFs from Slideshare presentations"
 
     parser = argparse.ArgumentParser(description=descr)
@@ -18,13 +21,22 @@ def parse_args():
                         help='force the output file name')
 
     args = parser.parse_args()
+
+    # If the user doesn't specify an output filename, we'll deduce
+    # one from the URL. Here's an URL example:
+    # https://www.slideshare.net/FrisodeJong/iso-20022-for-dummies
+    #
+    # We're taking the path (`/FrisodeJong/iso-20022-for-dummies`),
+    # isolating the part after the second slash (the first slash
+    # always being at the first position), and appending `.pdf` to it.
     if not args.out:
         path = urllib.parse.urlparse(args.url[0]).path
         args.out = '%s.pdf'%path[path.find('/', 1) + 1:]
     return args
 
 def main():
-    """ Main function. """
+    """ Main function of the program.
+    Uses the global command-line arguments (not custom ones)! """
     args = parse_args()
 
     res = requests.get(args.url[0])