Cython Cheat Sheet Cython ( Is a C Extension to the Python Programming Language That Allows for Static Compi- Lation and Strong Type Declaration

Cython Cheat Sheet Cython (https://cython.org/) is a C extension to the Python programming language that allows for static compilation and strong type declaration. It’s aim is to speed up Python signiﬁcantly. Compiling Cython Class and function declaration

Jupyter notebooks (temporary) Classes: %load_ext cython cdef class import Cython TestClass(object): # making variables accessible from Python # write code using cython # using public: # run cell cdef public int # nb! print functions have to be used a,b cdef public double # %%cython has to be written c # to each cell using it def # %%cython -a outputs function documentation __init__(self): # (which parts are compiled to C self.a=0 # and which are Python) self.b=1 self.c= 3.14

%% cython Functions: cdef int multiplyWithOne(int x): x*=1; def functionExample(int x, float y): return x # function is callable from Python and Cython print(multiplyWithOne(9)) return y*x ... pyximport (temporary) cdef functionExample(int x, float y): 1. write a file.pyx containing the source code # function is callable from Cython only 2. import (and autocompile) file.pyx using pyximport: # function is optimized return y*x # using pyximport for auto-compilation import pyximport cpdef functionExample(int x, float y): pyximport.install() # function is callable from Cython (optimized) import file #imports file.pyx # function is callable from Python (unoptimized) setup.py script return y*x 1. write a file.pyx containing the source code 2. compile it using a setup.py file containing: Further, the return type can be added to the function: from distutils.core import setup from Cython.Build import cythonize cdef float functionExample(int x, float y): # function is optimized & callable from Cython only setup(ext_modules= cythonize( ``file.pyx'')) return y*x 3. compile it: $ python setupy.py build_ext --inplace Type declaration Files .pyx Source code containing Cython code Cython offers static typing of the following types: .c C source code generated from .pyx file int A = 1 integer .so shared object file from compilation float A = 1.0 floating point (fp) .html documentation from %%cython -a double A = 1.0 double precision fp ./build/ temporary files from compilation char *A = ’1’ string (pointer (*)!!) Py_ssize_t signed integer for NumPy indices Misc Memory management Calling external C functions cdef extern from ''file.h'': Manual memory management can be done by importing double someFunctionsName(double) memory handling functions from the C standard library: from libc.math cimport cos void* malloc cdef double functionName(double x) void* realloc return cos(x) void free