.. highlightlang:: c

.. _complexobjects:

Complex Number Objects
----------------------

.. index:: object: complex number

Python's complex number objects are implemented as two distinct types when
viewed from the C API:  one is the Python object exposed to Python programs, and
the other is a C structure which represents the actual complex number value.
The API provides functions for working with both.


Complex Numbers as C Structures
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Note that the functions which accept these structures as parameters and return
them as results do so *by value* rather than dereferencing them through
pointers.  This is consistent throughout the API.


.. ctype:: Py_complex

   The C structure which corresponds to the value portion of a Python complex
   number object.  Most of the functions for dealing with complex number objects
   use structures of this type as input or output values, as appropriate.  It is
   defined as::

      typedef struct {
         double real;
         double imag;
      } Py_complex;


.. cfunction:: Py_complex _Py_c_sum(Py_complex left, Py_complex right)

   Return the sum of two complex numbers, using the C :ctype:`Py_complex`
   representation.


.. cfunction:: Py_complex _Py_c_diff(Py_complex left, Py_complex right)

   Return the difference between two complex numbers, using the C
   :ctype:`Py_complex` representation.


.. cfunction:: Py_complex _Py_c_neg(Py_complex complex)

   Return the negation of the complex number *complex*, using the C
   :ctype:`Py_complex` representation.


.. cfunction:: Py_complex _Py_c_prod(Py_complex left, Py_complex right)

   Return the product of two complex numbers, using the C :ctype:`Py_complex`
   representation.


.. cfunction:: Py_complex _Py_c_quot(Py_complex dividend, Py_complex divisor)

   Return the quotient of two complex numbers, using the C :ctype:`Py_complex`
   representation.


.. cfunction:: Py_complex _Py_c_pow(Py_complex num, Py_complex exp)

   Return the exponentiation of *num* by *exp*, using the C :ctype:`Py_complex`
   representation.


Complex Numbers as Python Objects
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^


.. ctype:: PyComplexObject

   This subtype of :ctype:`PyObject` represents a Python complex number object.


.. cvar:: PyTypeObject PyComplex_Type

   This instance of :ctype:`PyTypeObject` represents the Python complex number
   type. It is the same object as :class:`complex` in the Python layer.


.. cfunction:: int PyComplex_Check(PyObject *p)

   Return true if its argument is a :ctype:`PyComplexObject` or a subtype of
   :ctype:`PyComplexObject`.


.. cfunction:: int PyComplex_CheckExact(PyObject *p)

   Return true if its argument is a :ctype:`PyComplexObject`, but not a subtype of
   :ctype:`PyComplexObject`.


.. cfunction:: PyObject* PyComplex_FromCComplex(Py_complex v)

   Create a new Python complex number object from a C :ctype:`Py_complex` value.


.. cfunction:: PyObject* PyComplex_FromDoubles(double real, double imag)

   Return a new :ctype:`PyComplexObject` object from *real* and *imag*.


.. cfunction:: double PyComplex_RealAsDouble(PyObject *op)

   Return the real part of *op* as a C :ctype:`double`.


.. cfunction:: double PyComplex_ImagAsDouble(PyObject *op)

   Return the imaginary part of *op* as a C :ctype:`double`.


.. cfunction:: Py_complex PyComplex_AsCComplex(PyObject *op)

   Return the :ctype:`Py_complex` value of the complex number *op*.

   If *op* is not a Python complex number object but has a :meth:`__complex__`
   method, this method will first be called to convert *op* to a Python complex
   number object.
