Cython/python - List of cdef class

Question

I am trying to improve this code which uses list type :

# CLASS ORDERC #
################
cdef class OrderC:
    cdef int _side
    cdef float _px
    cdef int _vo

    def __cinit__(self, int side, float px, int vo):
        # ....

    cdef setData(self, double[:] dates):
        # ....

# CLASS LISTORDERC #
####################
cdef class ListOrderC:
    cdef int _B
    cdef list _LO_Bid

    cdef double[:] _dates

    def __init__(self, num.ndarray[num.double_t, ndim=1] dates):
        self._B = 0
        self._LO_Bid = []
        self._dates = dates

    cpdef addOrder(self, OrderC oo):
       self._B += 1
       self._LO_Bid.append(oo)
       self._LO_Bid[-1].setData(self._dates)

The problem arrives when i call addOrder from python :

 AttributeError: 'OrderC.OrderC' object has no attribute 'setData'

I guess it's because OrderC is recognized as python object, so I have to define setData with cpdef. But I want OrderC to be recognized as the cdef class to imporve the performance.

Could you please help me ?

Thanks

In the code you posted, the methods are not indented correctly. You just define a free function setData() independently from OrderC. You need to format the classes like you normal Python classes. — sth
– sth, Commented Sep 10, 2014 at 12:53
Yes, it is a mistake on the post only. In my code, the indentation is correct. I made corrections to this post. — MiKL
– MiKL, Commented Sep 10, 2014 at 13:05
Related 1) arrays of cdef class 2) About AttributeErrors when looking up classes in lists: stackoverflow.com/questions/66067323/… stackoverflow.com/questions/55230665/… — DavidW
– DavidW, Commented Mar 26, 2021 at 9:20

Veedrac · Accepted Answer · 2014-09-10 19:39:29Z

1

The problem is that list only holds things of type object, so when you access you get back an object.

You probably want to use a C++ vector instead.

answered Sep 10, 2014 at 19:39

Veedrac

60.7k15 gold badges120 silver badges177 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

sebdelsol Over a year ago

I was wondering whether cdef OrderC orderc = self._LO_Bid[-1] and orderc.setData(...) would work ?

Veedrac Over a year ago

Probably, but it's also likely to be slower because it has to check the types match and then unpack it. You can do unchecked casts, but even then a vector will be faster.

MiKL Over a year ago

Sebdel's solution works but performs a bit slower than my current solution. Cython doesn't let me compile a vector of OrderC pointer cdef vector<OrderC*> but not cdef public vector<OrderC*>. So I think that it will slow down my code since I will have to cast it as python object every time I wnat to acces it from python.

Veedrac Over a year ago

If you want fast access from Python as well, you could make every OrderC store object pointers to itself and return those on access from Python. No guarantees it'll work, but I don't see why it wouldn't.

Collectives™ on Stack Overflow

Cython/python - List of cdef class

1 Answer 1

4 Comments

Your Answer

Linked

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

4 Comments

Your Answer

Sign up or log in

Post as a guest

Linked

Related