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gh-115177: Clarify impact of -O and optimization in assert statement documentation #119305

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gh-115177: Clarify impact of -O and optimization in assert statement documentation #119305

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gh-115177: Mention PYTHONOPTIMIZE environment variable disables asser…
NXPY123 May 21, 2024
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gh:115177: Add Note to assert statement docs warning about possible i…
NXPY123 May 21, 2024
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gh-115177: Add line break to align text in assert statement doc
NXPY123 May 21, 2024
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gh-115177: Add line break to align text in assert statement doc
NXPY123 May 22, 2024
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10 changes: 9 additions & 1 deletion Doc/reference/simple_stmts.rst
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Expand Up @@ -404,12 +404,20 @@ The extended form, ``assert expression1, expression2``, is equivalent to ::
These equivalences assume that :const:`__debug__` and :exc:`AssertionError` refer to
the built-in variables with those names. In the current implementation, the
built-in variable :const:`__debug__` is ``True`` under normal circumstances,
``False`` when optimization is requested (command line option :option:`-O`). The current
``False`` when optimization is requested (command line option :option:`-O`
or environment variable :envvar:`PYTHONOPTIMIZE`). The current
code generator emits no code for an assert statement when optimization is
requested at compile time. Note that it is unnecessary to include the source
code for the expression that failed in the error message; it will be displayed
as part of the stack trace.

.. note::

It is considered good practice to not use :keyword:`assert` statements in
critical code logic while writing library code as enabling optimization will
cause the statements to be ignored. Evaluating function variables using
:keyword:`assert` statements can also lead to unexpected behavior.

Assignments to :const:`__debug__` are illegal. The value for the built-in variable
is determined when the interpreter starts.

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