How do I import function from .pyx file in python?

Question

I'm trying to run Hadoopy, which has a file _main.pyx, and import _main is failing with module not found in __init__.py.

I'm trying to run this on OS X w/ standard python 2.7.

Harmon

Answer 1

Add this code before you try to import _main:

import pyximport
pyximport.install()

Note that pyximport is part of Cython, so you'll have to install that if it isn't already.

Demetricedemetris

I don't have that module installed. I downloaded some files from prescod.net/pyximport, and then it says I need Pyrex.Distutils. Before I keep digging around for libraries, figured check to see if I'm missing something obvious (i.e. install cython or some other library/app/package) – Harmon

@dolan: Yes, you'll need Cython. I assumed you already had it installed as your question was tagged with it. – Demetricedemetris

To install Cython you have 3 options: 1. Run pip install Cython or 2. Goto cython.org., download it and run python setup.py install or 3. Run pip install Cython --install-option="--no-cython-compile" – Cantu

This still results in a has no attribute {function name} for me. My .pyx is cythonized python from which I am able to get a .so and .c file. – Froh

hey @Froh , have you got the problem solved? – Barca

Answer 2

You need to make sure you have followed all steps:

1. Install the Cython package using pip

   pip install Cython
   

2. Create a Cython file bbox.pyx

   cimport cython
   import numpy as np
   cimport numpy as np
   
   DTYPE = np.float32
   ctypedef np.float32_t DTYPE_t
   
   @cython.boundscheck(False)
   def compare_bboxes(
          np.ndarray[DTYPE_t, ndim=2] boxes1,
          np.ndarray[DTYPE_t, ndim=2] boxes2):
    ...
   

3. Create setup.py in the same directory

   from distutils.core import setup, Extension
   from Cython.Build import cythonize
   import numpy
   
   package = Extension('bbox', ['bbox.pyx'], include_dirs=[numpy.get_include()])
   setup(ext_modules=cythonize([package]))
   

4. Build the Cython

   python3 setup.py build_ext --inplace
   

5. Create your main python script run.py in the same directory

   import pyximport
   pyximport.install(setup_args={"script_args" : ["--verbose"]})
   from bbox import compare_bboxes
   
   def main(args):
      boxes1 = args.boxes1
      boxes2 = args.boxes2
      result = compare_bboxes(boxes1, boxes2)
   

6. Run your main script in the same directory

   python run.py
   

Cantu

nice answer; how to solve the case where the main script is not in the same directory of cython module? solved: add to main script: import pyximport pyximport.install() – Alligator