guess_all_extensions(): Return the empty list instead of None when

there are no matching types.  Updated the docs and docstrings.  Added
some unit tests.

1 files changed, 6 insertions, 9 deletions

diff --git a/Lib/mimetypes.py b/Lib/mimetypes.py
index a909366..5784e23 100644
--- a/Lib/mimetypes.py
+++ b/Lib/mimetypes.py
@@ -148,10 +148,8 @@ class MimeTypes:
 
         Return value is a list of strings giving the possible filename
         extensions, including the leading dot ('.').  The extension is not
-        guaranteed to have been associated with any particular data
-        stream, but would be mapped to the MIME type `type' by
-        guess_type().  If no extension can be guessed for `type', None
-        is returned.
+        guaranteed to have been associated with any particular data stream,
+        but would be mapped to the MIME type `type' by guess_type().
 
         Optional `strict' argument when false adds a bunch of commonly found,
         but non-standard types.
@@ -162,8 +160,7 @@ class MimeTypes:
             for ext in self.types_map_inv[False].get(type, []):
                 if ext not in extensions:
                     extensions.append(ext)
-        if len(extensions):
-            return extensions
+        return extensions
 
     def guess_extension(self, type, strict=True):
         """Guess the extension for a file based on its MIME type.
@@ -179,9 +176,9 @@ class MimeTypes:
         but non-standard types.
         """
         extensions = self.guess_all_extensions(type, strict)
-        if extensions is not None:
-            extensions = extensions[0]
-        return extensions
+        if not extensions:
+            return None
+        return extensions[0]
 
     def read(self, filename, strict=True):
         """