Interactive python and C (ctypes library)
ctypes is an external Python library, you can use python callable already compiled C language functions and data types and data exchange. ctypes official documents in https://docs.python.org/3/library/ctypes.html
1. ctypes basic data types map
2. python call the library c language
1. Generate c language function
#Step 1: test.c
#include <stdio.h>
the Add int (int A, int B)
{
return A + B;
}
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2. libtest.so compiler generates dynamic link library file (DLL)
-fPIC -shared -o libtest.so test.c gcc
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3. call DLL files
#Step 3: test.py
from ctypes import *
mylib = CDLL ( "libtest.so") or cdll.LoadLibrary ( "libtest.so")
the Add = mylib.add
add.argtypes = [c_int, c_int] # parameter types, two int (c_int is ctypes type, supra table)
add.restype = # c_int return type, int (c_int is ctypes type, see table above)
SUM = the Add (. 3,. 6)
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3. pointers and references
For instance pointer assignment would only change the memory address to which it points, rather than changing the contents of memory. Examples pointer contents have a property that returns an object pointer points to.
Function Description
byref (x [, offset]) Returns the address x, x must be an instance ctypes type. Corresponds to the c & x. offset is the offset.
pointer (x) creates and returns a pointer points to an instance of x, x is an instance object.
The POINTER (type) a return type, which is a pointer to the type of type pointer type, a type of ctypes type.
Import ctype * from
I c_int = (. 1)
PI = POINTER (c_int) (I)
PI2 = pointer (I)
Print # pi.contents object returns a pointer value
Print pi2.contents
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pointer and a POINTER The difference is, pointer returns an instance, pOINTER a return type.
4. The data structure type
Structures and Unions must inherit Structure and Union base classes that are defined in the ctypes module, each subclass must define a property fields, fields is a two-dimensional list of tuples, contain the name and type of each field, and this field type must be a ctypes type, such as c_int, or any other type of inheritance ctypes, such as Structure, Union, Array, pointer or the like.
* ctypes Import from
Import types
class the Test (Structure):
the _fields_ = [( 'X', c_int),
( 'Y', c_char)]
test1 the Test = (. 1, 2)
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. The structure for when the operation list, i.e. contains a pointer pointing to the structure, need to be defined as follows
from ctypes import *
import types
class Test(Structure):
pass
Test._fields_ = [('x', c_int),
('y', c_char),
('next', POINTER(Test))]
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参考文献：
1. http://blog.csdn.net/jsky_studio/article/details/38597655
2. http://blog.csdn.net/linda1000/article/details/12623527
3. https://www.cnblogs.com/night-ride-depart/p/4907613.html
It is noted that: more portions of text and the code reference from reference, if in doubt, references to view detailed explanation.
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