FAQ cdef_derive - cython/cython GitHub Wiki

Note that this example further down is outdated as of Cython 0.14. Do not do this! Instead, inherit from the normal Python type, e.g.

# Cython 0.14 and later

cdef class ObjectList(list):
    def foo(self):
        return list(self)

For Pyrex and older Cython versions, here is an example from Greg Ewing illustrating deriving from a builtin type (using the sage notebook):

%cython

cdef extern from "listobject.h":
    ctypedef class __builtin__.list [object PyListObject]:
        pass

cdef class ObjectList(list):
    def foo(self):
        return list(self)

v = ObjectList([1,2,3])

type(v.foo())
///
<type 'list'>

Note that you cannot subtype neither PyStringObject (__builtin__.str) this way, as it will break the way the string is allocated by Python, nor PyTupleObject (__builtin__.tuple).