pytest-dev/pytest · error · ImportPathMismatchError

( , , )

Error message

({module_name}, {module_file}, {path})

What it means

Raised by import_path (prepend/append modes) when the imported module's __file__ is None (lines 648-650). After importlib.import_module succeeds, the helper checks mod.__file__; a None file (typical of namespace packages or built-in modules) cannot be matched against the collected path, so ImportPathMismatchError is raised to avoid silently testing the wrong code.

Solutions

1. Switch to importlib import mode: --import-mode=importlib.
2. Add __init__.py to make the package a regular package with a real __file__.
3. Rename the colliding module to avoid shadowing a namespace/builtin.

Example fix

// before
pytest --import-mode=prepend
// after
pytest --import-mode=importlib

import importlib
mod = importlib.import_module(module_name)
if getattr(mod, '__file__', None) is None:
    # will mismatch; choose importlib mode or add __init__.py

def _module_has_file(modname) -> bool:
    import importlib
    return getattr(importlib.import_module(modname), '__file__', None) is not None

When it happens

Trigger: Collecting a file that resolves to a namespace package (no __init__.py) whose __file__ is None; a module shadowed by a built-in or C extension; __init__.py-less package layouts combined with prepend import mode.

Common situations: Namespace packages in prepend/append mode; mixing importlib and prepend modes; a local file name colliding with a stdlib module.

Related errors

• Can't find module at location
• Could not resolve for
• {path}
• cannot create lockfile in
• cannot delete key in keywords dict

AI-assisted analysis of pytest-dev/pytest@0d6fbdeffa (2026-08-11). Data as JSON: /api/errors/63557d91b8f84bfe. Report an issue: GitHub.

Appendix: source

Thrown at src/_pytest/pathlib.py:650

        if str(pkg_root) not in sys.path:
            sys.path.append(str(pkg_root))
    elif mode is ImportMode.prepend:
        if str(pkg_root) != sys.path[0]:
            sys.path.insert(0, str(pkg_root))
    else:
        assert_never(mode)

    importlib.import_module(module_name)

    mod = sys.modules[module_name]
    if path.name == "__init__.py":
        return mod

    ignore = os.environ.get("PY_IGNORE_IMPORTMISMATCH", "")
    if ignore != "1":
        module_file = mod.__file__
        if module_file is None:
            raise ImportPathMismatchError(module_name, module_file, path)

        if module_file.endswith((".pyc", ".pyo")):
            module_file = module_file[:-1]
        if module_file.endswith(os.sep + "__init__.py"):
            module_file = module_file[: -(len(os.sep + "__init__.py"))]

        try:
            is_same = _is_same(str(path), module_file)
        except FileNotFoundError:
            is_same = False

        if not is_same:
            raise ImportPathMismatchError(module_name, module_file, path)

    return mod


def _import_module_using_spec(

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