Share Cython installation and usage experience

1. What is Cython?

It is a tool used to quickly generate Python extension module (extension module) tool

its syntax is a mixture of python language syntax and c language syntax

him It is easier to write python extension modules than swig

Maybe you will say that swig can generate extension modules directly through c header files, but swig's support for callback functions is not very good,

In addition, if you use swig, in many cases, you have to write additional code to convert the input parameters into python objects and convert the output into python objects, for example, if you encapsulate a C function If the parameters are input and output, and if there is a callback function in the parameters of the C function,

and in Cython, the types in C, such as int, float, long, char*, etc. will all Automatically convert to python objects when necessary, or convert from python objects to C types. When the conversion fails, an exception will be thrown . This is the most amazing thing about Cython

In addition, Cython also has good support for callback functions.

In short, if you have the need to write python extension modules, then Cython is really a good tool

2. Convert to cython

cython Installation under linux:

1. Source package installation:

[blueelwang@pythontab ~]$ wget https://pypi.python.org/packages/b7/67/7e2a817f9e9c773ee3995c1e15204f5d01c8da71882016cac10342ef031b/Cython-0.25.2.tar.gz
[blueelwang@pythontab ~]$ tar xzvf Cython-0.25.2.tar.gz
[blueelwang@pythontab ~]$ cd Cython-0.25.2
[blueelwang@pythontab ~]$ python setup.py install

2. pip package installation

[blueelwang@pythontab ~]$ sudo pip install Cython --install-option="--no-cython-compile"

3. Installation under Ubuntu

[blueelwang@pythontab ~]$ sudo apt-get install cython

After installation, enter cython to verify whether the installation is successful

3. Use

1. Write with .pyx as extension cython program, hello.pyx

def say_hello_to(name):
    print("Hello %s!" % name)

2. Write the python program setup.py

The purpose is to convert the hello.pyx program into hello.c and compile it into an so file

from distutils.core import setup
from distutils.extension import Extension
from Cython.Distutils import build_ext
ext_modules = [Extension("hello", ["hello.pyx"])]
setup(
  name = 'Hello world app',
  cmdclass = {'build_ext': build_ext},
  ext_modules = ext_modules
)

3. Execute the python program

[blueelwang@pythontab ~]$ python setup.py build_ext --inplace

The execution result will generate two files: hello.c and hello.so (files encapsulated with PyObject*)

4. Use python to call hello.so, and the calling file is test.py

import hello
hello.say_hello_to("hi,cython!!")

The main purpose of cython is to: Simplify the cumbersome encapsulation process of python calling c language programs, and improve the execution speed of python code (C The execution speed of the language is faster than python)

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