pytest-dev/pytest · error · ImportPathMismatchError

{module_name}, {module_file}, {path}

Error message

{module_name}, {module_file}, {path}

What it means

In prepend/append import mode, after importing the module pytest compares its __file__ against the requested path. If module.__file__ is None (the module has no on-disk file, e.g. a built-in, frozen, or namespace module), it raises ImportPathMismatchError to avoid silently binding the wrong module.

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(

View on GitHub (pinned to 98b357f69e)

Solutions

1. Set PY_IGNORE_IMPORTMISMATCH=1 to skip the mismatch check
2. Rename the file so its module name does not collide with a built-in/frozen module
3. Fix the package layout so the module resolves to a real .py file

Example fix

// before
# file named enum.py colliding with stdlib enum
// after
mv tests/enum.py tests/test_enum.py

import os
def should_skip_mismatch_check():
    return os.environ.get('PY_IGNORE_IMPORTMISMATCH', '') == '1'

try:
    mod = import_path(path, mode='prepend')
except ImportPathMismatchError:
    os.environ['PY_IGNORE_IMPORTMISMATCH'] = '1'
    mod = import_path(path, mode='prepend')

When it happens

Trigger: import_path in prepend/append mode resolves module_name to a module whose __file__ is None, then tries the mismatch check at pathlib.py:648-650 and raises. PY_IGNORE_IMPORTMISMATCH is not set.

Common situations: A test/conftest file whose name collides with a built-in or frozen module; namespace package resolving to a module without a file; exotic import hooks.

Related errors

• Can't find module {module_name} at location {path}
• {path}
• --pdbcls: could not import {value!r}: {exc}
• module or package not found: {arg} (missing __init__.py?)
• import error in {used}: {ex}

AI-assisted analysis of pytest-dev/pytest@98b357f69e (2026-08-04). Data as JSON: /data/errors/0bbe69afd994aa06.json. Report an issue: GitHub.