run Cython in Jupyter cdef

Question

I am looking for incorporate some cython to speed my code. I get a issue with running cython code in Jupyter.

cell 1:

%%cython
cdef fuc():
    cdef int a = 0
    for i in range(10):
        a += i
        print(a)

cell 2:

fuc()

error:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
<ipython-input-48-10789e9d47b8> in <module>()
----> 1 fuc()

NameError: name 'fuc' is not defined

but if i do this, it works fine.

%%cython
def fuc():
    cdef int a = 0
    for i in range(10):
        a += i
        print(a)

Looks like cdef is using differently in Jupyter, how could I use cdef in Jupyter notebook?

Answer 1

cdef functions can only be called from Cython, not Python. The documentation says

Within a Cython module, Python functions and C functions can call each other freely, but only Python functions can be called from outside the module by interpreted Python code.

(having already stated that "C functions" are defined by cdef and "Python functions" by def.)

Use a def function in Cython instead. It's still compiled by Cython. You can still cdef types within your def function.