.. _consider-math-not-float:

consider-math-not-float / R6106
===============================

**Message emitted:**

``Consider %smath.%s instead of %s``

**Description:**

*Using math.inf or math.nan permits to benefit from typing and it is up to 4 times faster than a float call (after the initial import of math). This check also catches typos in float calls as a side effect.*

**Problematic code:**

.. literalinclude:: /data/messages/c/consider-math-not-float/bad.py
   :language: python

**Correct code:**

.. literalinclude:: /data/messages/c/consider-math-not-float/good.py
   :language: python

**Configuration file:**

.. literalinclude:: /data/messages/c/consider-math-not-float/pylintrc
    :language: ini

**Additional details:**

This is an extension check because the typing advantage could be fixed.

Regarding performance, float("nan") and float("inf") are slower than their counterpart math.inf and math.nan by a factor of 4 after the initial import of math.

.. code-block:: python

    import math
    import timeit

    time_math_inf = timeit.timeit('math.nan', globals=globals(), number=10**8)
    print(f'math.nan: {time_math_inf:.2f} seconds')

    import timeit
    time_inf_str = timeit.timeit('float("nan")', number=10**8)
    print(f'float("nan"): {time_inf_str:.2f} seconds')

Result::

    math.nan: 1.24 seconds
    float("nan"): 5.15 seconds

But if we take the initial import into account it's worse.

.. code-block:: python

    import timeit

    time_math_inf = timeit.timeit('import math;math.nan', globals=globals(), number=10**8)
    print(f'math.nan: {time_math_inf:.2f} seconds')

    import timeit
    time_inf_str = timeit.timeit('float("nan")', number=10**8)
    print(f'float("nan"): {time_inf_str:.2f} seconds')

Result::

    math.nan: 9.08 seconds
    float("nan"): 5.33 seconds

So the decision depends on how and how often you need to use it and what matter to you.




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

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