add 'ext_from_url' to text.py

gallery_dl/text.py

@@ -55,15 +55,22 @@ def split_html(txt, sep=None):
 
 
 def filename_from_url(url):
-    """Extract the last part of an url to use as a filename"""
+    """Extract the last part of an URL to use as a filename"""
     try:
         return urllib.parse.urlsplit(url).path.rpartition("/")[2]
     except (TypeError, AttributeError):
         return ""
 
 
+def ext_from_url(url):
+    """Extract the filename extension of an URL"""
+    filename = filename_from_url(url)
+    ext = os.path.splitext(filename)[1]
+    return ext[1:].lower()
+
+
 def nameext_from_url(url, data=None):
-    """Extract the last part of an url and fill 'data' accordingly"""
+    """Extract the last part of an URL and fill 'data' accordingly"""
     if data is None:
         data = {}
     data["filename"] = unquote(filename_from_url(url))

test/test_text.py

@@ -105,6 +105,22 @@ class TestText(unittest.TestCase):
         for value in INVALID:
             self.assertEqual(f(value), "")
 
+    def test_ext_from_url(self, f=text.ext_from_url):
+        result = "ext"
+
+        # standard usage
+        self.assertEqual(f(""), "")
+        self.assertEqual(f("filename.ext"), result)
+        self.assertEqual(f("/filename.ext"), result)
+        self.assertEqual(f("example.org/filename.ext"), result)
+        self.assertEqual(f("http://example.org/v2/filename.ext"), result)
+        self.assertEqual(
+            f("http://example.org/v2/filename.ext?param=value#frag"), result)
+
+        # invalid arguments
+        for value in INVALID:
+            self.assertEqual(f(value), "")
+
     def test_nameext_from_url(self, f=text.nameext_from_url):
         empty = {"filename": "", "name": "", "extension": ""}
         result = {"filename": "filename.ext",