urlresolvers.py 文件源码

def get_callable(lookup_view, can_fail=False):
    """
    Convert a string version of a function name to the callable object.

    If the lookup_view is not an import path, it is assumed to be a URL pattern
    label and the original string is returned.

    If can_fail is True, lookup_view might be a URL pattern label, so errors
    during the import fail and the string is returned.
    """
    if not callable(lookup_view):
        mod_name, func_name = get_mod_func(lookup_view)
        if func_name == '':
            return lookup_view

        try:
            mod = import_module(mod_name)
        except ImportError:
            parentmod, submod = get_mod_func(mod_name)
            if (not can_fail and submod != '' and
                    not module_has_submodule(import_module(parentmod), submod)):
                raise ViewDoesNotExist(
                    "Could not import %s. Parent module %s does not exist." %
                    (lookup_view, mod_name))
            if not can_fail:
                raise
        else:
            try:
                lookup_view = getattr(mod, func_name)
                if not callable(lookup_view):
                    raise ViewDoesNotExist(
                        "Could not import %s.%s. View is not callable." %
                        (mod_name, func_name))
            except AttributeError:
                if not can_fail:
                    raise ViewDoesNotExist(
                        "Could not import %s. View does not exist in module %s." %
                        (lookup_view, mod_name))
    return lookup_view