diff --git a/scripts/update_lib/cmd_todo.py b/scripts/update_lib/cmd_todo.py
index 2d5685fdd50..4f893c52801 100644
--- a/scripts/update_lib/cmd_todo.py
+++ b/scripts/update_lib/cmd_todo.py
@@ -334,7 +334,7 @@ def compute_test_todo_list(
             test_order = lib_test_order[lib_name].index(test_name)
         else:
             # Extract lib name from test name (test_foo -> foo)
-            lib_name = test_name.removeprefix("test_").removeprefix("_test")
+            lib_name = test_name.removeprefix("test_")
             test_order = 0  # Default order for tests not in DEPENDENCIES
 
         # Check if corresponding lib is up-to-date
diff --git a/scripts/update_lib/deps.py b/scripts/update_lib/deps.py
index e12c6d24965..cc169f2ff7a 100644
--- a/scripts/update_lib/deps.py
+++ b/scripts/update_lib/deps.py
@@ -11,6 +11,7 @@
 import difflib
 import functools
 import pathlib
+import re
 import shelve
 import subprocess
 
@@ -31,98 +32,62 @@
 # === Import parsing utilities ===
 
 
-class ImportVisitor(ast.NodeVisitor):
-    def __init__(self) -> None:
-        self.test_imports = set()
-        self.lib_imports = set()
+def _extract_top_level_code(content: str) -> str:
+    """Extract only top-level code from Python content for faster parsing."""
+    def_idx = content.find("\ndef ")
+    class_idx = content.find("\nclass ")
 
-    def add_import(self, name: str) -> None:
-        """
-        Add an `import` to its correct slot (`test_imports` or `lib_imports`).
+    indices = [i for i in (def_idx, class_idx) if i != -1]
+    if indices:
+        content = content[: min(indices)]
+    return content.rstrip("\n")
 
-        Parameters
-        ----------
-        name : str
-            Module name.
-        """
-        if name.startswith("test.support"):
-            return
 
-        real_name = name.split(".", 1)[-1]
-        if name.startswith("test."):
-            self.test_imports.add(real_name)
-        else:
-            self.lib_imports.add(real_name)
-
-    def visit_Import(self, node):
-        for alias in node.names:
-            self.add_import(alias.name)
-
-    def visit_ImportFrom(self, node):
-        try:
-            module = node.module
-        except AttributeError:
-            # Ignore `from . import my_internal_module`
-            return
-
-        for name in node.names:
-            self.add_import(f"{module}.{name}")
-
-    def visit_Call(self, node) -> None:
-        """
-        In test files, there's sometimes use of:
-
-        ```python
-        import test.support
-        from test.support import script_helper
-
-        script = support.findfile("_test_atexit.py")
-        script_helper.run_test_script(script)
-        ```
-
-        This imports "_test_atexit.py" but does not show as an import node.
-        """
-        func = node.func
-        if not isinstance(func, ast.Attribute):
-            return
+_FROM_TEST_IMPORT_RE = re.compile(r"^from test import (.+)", re.MULTILINE)
+_FROM_TEST_DOT_RE = re.compile(r"^from test\.(\w+)", re.MULTILINE)
+_IMPORT_TEST_DOT_RE = re.compile(r"^import test\.(\w+)", re.MULTILINE)
 
-        value = func.value
-        if not isinstance(value, ast.Name):
-            return
 
-        if (value.id != "support") or (func.attr != "findfile"):
-            return
+def parse_test_imports(content: str) -> set[str]:
+    """Parse test file content and extract test package dependencies."""
+    content = _extract_top_level_code(content)
+    imports = set()
 
-        arg = node.args[0]
-        if not isinstance(arg, ast.Constant):
-            return
+    for match in _FROM_TEST_IMPORT_RE.finditer(content):
+        import_list = match.group(1)
+        for part in import_list.split(","):
+            name = part.split()[0].strip()
+            if name and name not in ("support", "__init__"):
+                imports.add(name)
 
-        target = arg.value
-        if not target.endswith(".py"):
-            return
+    for match in _FROM_TEST_DOT_RE.finditer(content):
+        dep = match.group(1)
+        if dep not in ("support", "__init__"):
+            imports.add(dep)
 
-        target = target.removesuffix(".py")
-        self.add_import(f"test.{target}")
+    for match in _IMPORT_TEST_DOT_RE.finditer(content):
+        dep = match.group(1)
+        if dep not in ("support", "__init__"):
+            imports.add(dep)
 
+    return imports
 
-def parse_test_imports(content: str) -> set[str]:
-    """Parse test file content and extract test package dependencies."""
-    if not (tree := safe_parse_ast(content)):
-        return set()
 
-    visitor = ImportVisitor()
-    visitor.visit(tree)
-    return visitor.test_imports
+_IMPORT_RE = re.compile(r"^import\s+(\w[\w.]*)", re.MULTILINE)
+_FROM_IMPORT_RE = re.compile(r"^from\s+(\w[\w.]*)\s+import", re.MULTILINE)
 
 
 def parse_lib_imports(content: str) -> set[str]:
     """Parse library file and extract all imported module names."""
-    if not (tree := safe_parse_ast(content)):
-        return set()
+    imports = set()
 
-    visitor = ImportVisitor()
-    visitor.visit(tree)
-    return visitor.lib_imports
+    for match in _IMPORT_RE.finditer(content):
+        imports.add(match.group(1))
+
+    for match in _FROM_IMPORT_RE.finditer(content):
+        imports.add(match.group(1))
+
+    return imports
 
 
 # === TODO marker utilities ===
@@ -139,7 +104,7 @@ def filter_rustpython_todo(content: str) -> str:
 
 def count_rustpython_todo(content: str) -> int:
     """Count lines containing RustPython TODO markers."""
-    return content.count(TODO_MARKER)
+    return sum(1 for line in content.splitlines() if TODO_MARKER in line)
 
 
 def count_todo_in_path(path: pathlib.Path) -> int:
@@ -148,7 +113,10 @@ def count_todo_in_path(path: pathlib.Path) -> int:
         content = safe_read_text(path)
         return count_rustpython_todo(content) if content else 0
 
-    return sum(count_rustpython_todo(content) for _, content in read_python_files(path))
+    total = 0
+    for _, content in read_python_files(path):
+        total += count_rustpython_todo(content)
+    return total
 
 
 # === Test utilities ===