Prerequisite: Using C codes in Python | Set 1
In the previous article, we have discussed how to access C code in Python. Now, let’s see how to access C functions.
Code #1 : Accessing C functions with Python
import work print ("GCD : ", work.gcd(35, 42)) print ("\ndivide : ", work.divide(42, 8)) print ("\navg : ", work.avg([1, 2, 3])) p1 = work.Point(1, 2) p2 = work.Point(4, 5) print ("\ndistance : ", work.distance(p1, p2)) |
Output :
GCD : 7 divide : (5, 2) avg : 2.0 distance : 4.242640687119285
Issue ?
Now the work done above has an issue that for the overall packaging of C and Python code together, using ctypes to access C code that has been compiled, one has to make sure that the shared library gets placed in a location, where the work.py module can find it. One possibility is to put the resulting libsample.so file in the same directory as the supporting Python code.
So, if the C library is installed elsewhere, then path has to be adjusted accordingly. If it is installed as a standard library on the machine, then ctypes.util.find_library() function can be used.
Code #2 : Path Example
from ctypes.util import find_library find_library('m') find_library('pthread') find_library('sample') |
Output :
/usr/lib/libm.dylib /usr/lib/libpthread.dylib /usr/local/lib/libsample.so
Again, ctypes won’t work at all if it can’t locate the library with the C code. ctypes.cdll.LoadLibrary() is used to load the C library, once it’s location is known.
_mod = ctypes.cdll.LoadLibrary(_path) |
