.. _use-set-for-membership:

use-set-for-membership / R6201
==============================

**Message emitted:**

``Consider using set for membership test``

**Description:**

*Membership tests are more efficient when performed on a lookup optimized datatype like ``sets``.*

**Problematic code:**

.. literalinclude:: /data/messages/u/use-set-for-membership/bad.py
   :language: python

**Correct code:**

.. literalinclude:: /data/messages/u/use-set-for-membership/good.py
   :language: python

**Configuration file:**

.. literalinclude:: /data/messages/u/use-set-for-membership/pylintrc
    :language: ini





.. note::
  This message is emitted by the optional :ref:`'set_membership'<pylint.extensions.set_membership>`
  checker, which requires the ``pylint.extensions.set_membership`` plugin to be loaded.

Created by the `set_membership <https://github.com/pylint-dev/pylint/blob/main/pylint/extensions/set_membership.py>`__ checker.