.. index:: py::builtins::assert

.. _doxycast_pypp_namespacepy_1_1builtins_1ac1925647ee1f0e5cb405d180e4587dbf:

.. _py-builtins-assert:

*py::builtins::*\ assert
========================

*Defined in* ``<pypp/builtins/assert.hpp>``

.. code-block:: cpp

     void assert(bool expression);                               // 1

     void assert(bool expression, std::string message);          // 2

1.   Assert an expression and throws on failure.

2.   Assert an expression and throws on failure with given message.

``py::builtins::assert`` asserts whether is given value is ``true``
(usually returned from an expression) and raises
:ref:`py-builtins-AssertionError` on failure.


Parameters
----------

``expression``: The expression to assert.

``message``: The message of exception message.


Complexity
----------

Constant.


Example
-------

.. code-block:: cpp

     #include <pypp/builtins/assert.hpp>
     #include <pypp/builtins/print.hpp>

     int main()
     {
         py::assert(true);

         try
         {
             py::assert(false);
         }
         catch (py::AssertionError&)
         {
             py::print("assert failed: py::assert(false)");
         }
     }

**Output**:

.. code-block:: text

     assert failed: py::assert(false)