This document describes the current stable version of Celery (5.2). For development docs, go here.

Source code for kombu.utils.imports

"""Import related utilities."""

import importlib
import sys

from kombu.exceptions import reraise


def symbol_by_name(name, aliases=None, imp=None, package=None,
                   sep='.', default=None, **kwargs):
    """Get symbol by qualified name.

    The name should be the full dot-separated path to the class::

        modulename.ClassName

    Example::

        celery.concurrency.processes.TaskPool
                                    ^- class name

    or using ':' to separate module and symbol::

        celery.concurrency.processes:TaskPool

    If `aliases` is provided, a dict containing short name/long name
    mappings, the name is looked up in the aliases first.

    Examples:
        >>> symbol_by_name('celery.concurrency.processes.TaskPool')
        <class 'celery.concurrency.processes.TaskPool'>

        >>> symbol_by_name('default', {
        ...     'default': 'celery.concurrency.processes.TaskPool'})
        <class 'celery.concurrency.processes.TaskPool'>

        # Does not try to look up non-string names.
        >>> from celery.concurrency.processes import TaskPool
        >>> symbol_by_name(TaskPool) is TaskPool
        True
    """
    aliases = {} if not aliases else aliases
    if imp is None:
        imp = importlib.import_module

    if not isinstance(name, str):
        return name                                 # already a class

    name = aliases.get(name) or name
    sep = ':' if ':' in name else sep
    module_name, _, cls_name = name.rpartition(sep)
    if not module_name:
        cls_name, module_name = None, package if package else cls_name
    try:
        try:
            module = imp(module_name, package=package, **kwargs)
        except ValueError as exc:
            reraise(ValueError,
                    ValueError(f"Couldn't import {name!r}: {exc}"),
                    sys.exc_info()[2])
        return getattr(module, cls_name) if cls_name else module
    except (ImportError, AttributeError):
        if default is None:
            raise
    return default