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Diffstat (limited to 'Doc/library/constants.rst')
| -rw-r--r-- | Doc/library/constants.rst | 12 |
1 files changed, 12 insertions, 0 deletions
diff --git a/Doc/library/constants.rst b/Doc/library/constants.rst index c36b2fa..634656a 100644 --- a/Doc/library/constants.rst +++ b/Doc/library/constants.rst @@ -5,6 +5,11 @@ Built-in Constants A small number of constants live in the built-in namespace. They are: +.. note:: + + :data:`None`, :data:`False`, :data:`True` and :data:`__debug__` cannot be + reassigned, so they can be considered "true" constants. + .. XXX False, True, None are keywords too .. data:: False @@ -37,3 +42,10 @@ A small number of constants live in the built-in namespace. They are: slicing syntax for user-defined container data types, as in :: val = container[1:5, 7:10, ...] + + +.. data:: __debug__ + + A boolean value that is :data:`True` if Python was not started with the + ``-O`` command line option. Its value is used indirectly by the + :keyword:`assert` statement, but it can also be used directly in code. |