.. _logging-not-lazy:

logging-not-lazy / W1201
========================

**Message emitted:**

``Use %s formatting in logging functions``

**Description:**

*Used when a logging statement has a call form of "logging.<logging method>(format_string % (format_args...))". Use another type of string formatting instead. You can use % formatting but leave interpolation to the logging function by passing the parameters as arguments. If logging-fstring-interpolation is disabled then you can use fstring formatting. If logging-format-interpolation is disabled then you can use str.format.*

**Problematic code:**

.. literalinclude:: /data/messages/l/logging-not-lazy/bad.py
   :language: python

**Correct code:**

.. literalinclude:: /data/messages/l/logging-not-lazy/good.py
   :language: python


**Additional details:**

Another reasonable option is to use f-strings. If you want to do that, you need to enable
``logging-not-lazy`` and disable ``logging-fstring-interpolation``.

**Related links:**

- `Logging variable data <https://docs.python.org/3/howto/logging.html#logging-variable-data>`_
- `Rationale for the message on stackoverflow <https://stackoverflow.com/a/34634301/2519059>`_


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