Remove duplicates while preserving order

spotdl/internals.py

@@ -180,3 +180,17 @@ def get_music_dir():
     # respectively is sufficient.
     # On Linux, default to /home/<user>/Music if the above method failed.
     return os.path.join(home, 'Music')
+
+
+def remove_duplicates(tracks):
+    """
+    Removes duplicates from a list whilst preserving order.
+
+    We could directly call `set()` on the list but it changes
+    the order of elements.
+    """
+
+    local_set = set()
+    local_set_add = local_set.add
+    return [x for x in tracks
+            if not (x in local_set or local_set_add(x))]

spotdl/spotdl.py

@@ -68,7 +68,7 @@ def download_list(text_file):
     with open(text_file, 'r') as listed:
         # read tracks into a list and remove any duplicates
         lines = listed.read().splitlines()
-        lines = list(set(lines))
+        lines = internals.remove_duplicates(lines)
     # ignore blank lines in text_file (if any)
     try:
         lines.remove('')