diff --git a/.github/workflows/lib-deps-check.yaml b/.github/workflows/lib-deps-check.yaml
index 9ef7943fe..66ecd46d7 100644
--- a/.github/workflows/lib-deps-check.yaml
+++ b/.github/workflows/lib-deps-check.yaml
@@ -50,35 +50,51 @@ jobs:
           persist-credentials: false
 
       - name: Get changed Lib files
-        id: changed-files
+        id: all-changed-files
         run: |
           # Get the list of changed files under Lib/
-          changed=$(git diff --name-only ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }} -- 'Lib/*.py' 'Lib/**/*.py' | head -50)
-          echo "Changed files:"
-          echo "$changed"
+          {
+            echo 'changed<<EOF'
 
-          # Extract unique module names
-          modules=""
-          for file in $changed; do
-            if [[ "$file" == Lib/test/* ]]; then
-              # Test files: Lib/test/test_pydoc.py -> test_pydoc, Lib/test/test_pydoc/foo.py -> test_pydoc
-              module=$(echo "$file" | sed -E 's|^Lib/test/||; s|\.py$||; s|/.*||')
-              # Skip non-test files in test/ (e.g., support.py, __init__.py)
-              if [[ ! "$module" == test_* ]]; then
+            git diff --name-only ${{ github.event.pull_request.base.sha }} ${{ github.event.pull_request.head.sha }} -- 'Lib/*.py' 'Lib/**/*.py'
+
+            echo 'EOF' 
+          } >> "$GITHUB_OUTPUT"
+
+      - name: Parse changed files
+        id: changed-files
+        run: |
+          from os import environ
+
+          files = environ["FILES"]
+          modules = set()
+          for file in files.splitlines():
+            file = file.strip()
+
+            if file.startswith("Lib/test/"):
+              # Test files:
+              # Lib/test/test_pydoc.py -> test_pydoc
+              # Lib/test/test_pydoc/foo.py -> test_pydoc
+              module = file.removeprefix("Lib/test/").split("/")[0]
+              if not module.startswith("test_"):
                 continue
-              fi
-            else
-              # Lib files: Lib/foo.py -> foo, Lib/foo/__init__.py -> foo
-              module=$(echo "$file" | sed -E 's|^Lib/||; s|/__init__\.py$||; s|\.py$||; s|/.*||')
-            fi
-            if [[ -n "$module" && " $modules " != *" $module "* ]]; then
-              modules="$modules $module"
-            fi
-          done
+            else:
+              # Lib files:
+              # Lib/foo.py -> foo
+              # Lib/foo/__init__.py -> foo
+              module = file.removeprefix("Lib/").split("/")[0]
+            
+            module = module.split(".")[0]
+            modules.add(module)
 
-          modules=$(echo "$modules" | xargs)  # trim whitespace
-          echo "Detected modules: $modules"
-          echo "modules=$modules" >> "$GITHUB_OUTPUT"
+          print(f"{modules=}")
+          output = " ".join(sorted(modules))
+          output_file = environ["GITHUB_OUTPUT"]
+          with open(output_file, mode="a", encoding="utf-8") as fd:
+            fd.write(f"modules={output}\n")
+        env:
+          FILES: ${{ steps.all-changed-files.outputs.changed }}
+        shell: python
 
       - name: Setup Python
         if: steps.changed-files.outputs.modules != ''
diff --git a/scripts/update_lib/cmd_deps.py b/scripts/update_lib/cmd_deps.py
index affb4b360..569cbfd0c 100644
--- a/scripts/update_lib/cmd_deps.py
+++ b/scripts/update_lib/cmd_deps.py
@@ -392,7 +392,7 @@ def show_deps(
     """Show all dependency information for modules."""
     # Expand "all" to all module names
     expanded_names = []
-    for name in names:
+    for name in set(names):
         if name == "all":
             expanded_names.extend(get_all_modules(cpython_prefix))
         else:
@@ -446,6 +446,11 @@ def main(argv: list[str] | None = None) -> int:
 
     args = parser.parse_args(argv)
 
+    # When user does `./update_lib/ deps "foo bar" "baz"`
+    # We still want to get a list of
+    # ["foo", "bar", "baz"], not ["foo bar", "baz"]
+    args.names = [name for names in args.names for name in names.split()]
+
     try:
         show_deps(args.names, args.cpython, args.lib, args.depth)
         return 0