Function import_fresh_module

Lib/test/support/import_helper.py:142–197

Import and return a module, deliberately bypassing sys.modules. This function imports and returns a fresh copy of the named Python module by removing the named module from sys.modules before doing the import. Note that unlike reload, the original module is not affected by this opera

(name, fresh=(), blocked=(), *,
                        deprecated=False,
                        usefrozen=False,
                        )

def import_fresh_module(name, fresh=(), blocked=(), *,
                        deprecated=False,
                        usefrozen=False,
                        ):
    """Import and return a module, deliberately bypassing sys.modules.

    This function imports and returns a fresh copy of the named Python module
    by removing the named module from sys.modules before doing the import.
    Note that unlike reload, the original module is not affected by
    this operation.

    *fresh* is an iterable of additional module names that are also removed
    from the sys.modules cache before doing the import. If one of these
    modules can't be imported, None is returned.

    *blocked* is an iterable of module names that are replaced with None
    in the module cache during the import to ensure that attempts to import
    them raise ImportError.

    The named module and any modules named in the *fresh* and *blocked*
    parameters are saved before starting the import and then reinserted into
    sys.modules when the fresh import is complete.

    Module and package deprecation messages are suppressed during this import
    if *deprecated* is True.

    This function will raise ImportError if the named module cannot be
    imported.

    If "usefrozen" is False (the default) then the frozen importer is
    disabled (except for essential modules like importlib._bootstrap).
    """
    # NOTE: test_heapq, test_json and test_warnings include extra sanity checks
    # to make sure that this utility function is working as expected
    with _ignore_deprecated_imports(deprecated):
        # Keep track of modules saved for later restoration as well
        # as those which just need a blocking entry removed
        fresh = list(fresh)
        blocked = list(blocked)
        names = {name, *fresh, *blocked}
        orig_modules = _save_and_remove_modules(names)
        for modname in blocked:
            sys.modules[modname] = None

        try:
            with frozen_modules(usefrozen):
                # Return None when one of the "fresh" modules can not be imported.
                try:
                    for modname in fresh:
                        __import__(modname)
                except ImportError:
                    return None
                return importlib.import_module(name)
        finally:
            _save_and_remove_modules(names)
            sys.modules.update(orig_modules)