Most Python/C API functions have one or more arguments as well as a
return value of type PyObject *
. This type is a pointer
(obviously!) to an opaque data type representing an arbitrary Python
object. Since all Python object types are treated the same way by the
Python language in most situations (e.g., assignments, scope rules,
and argument passing), it is only fitting that they should be
represented by a single C type. All Python objects live on the heap:
you never declare an automatic or static variable of type
PyObject
, only pointer variables of type PyObject *
can
be declared.
All Python objects (even Python integers) have a ``type'' and a
``reference count''. An object's type determines what kind of object
it is (e.g., an integer, a list, or a user-defined function; there are
many more as explained in the Python Language Reference Manual). For
each of the well-known types there is a macro to check whether an
object is of that type; for instance, PyList_Check(a)
is true
iff the object pointed to by a
is a Python list.