How can I use a DLL file from Python

Question

What is the easiest way to use a DLL file from within Python   Specifically  how can this be done without writing any additional wrapper C   code to expose the functionality to Python   Native Python functionality is strongly preferred over using a third-party library

User · Answer

Building a DLL and linking it under Python using ctypes

I present a fully worked example on how building a shared library and using it under Python by means of ctypes. I consider the Windows case and deal with DLLs. Two steps are needed:

Build the DLL using Visual Studio's compiler either from the command line or from the IDE;
Link the DLL under Python using ctypes.

The shared library

The shared library I consider is the following and is contained in the testDLL.cpp file. The only function testDLL just receives an int and prints it.

#include <stdio.h>
?
extern "C" {
?
__declspec(dllexport)
?
void testDLL(const int i) {
    printf("%d\n", i);
}
?
} // extern "C"

Building the DLL from the command line

To build a DLL with Visual Studio from the command line run

"C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\Tools\vsdevcmd"

to set the include path and then run

cl.exe /D_USRDLL /D_WINDLL testDLL.cpp /MT /link /DLL /OUT:testDLL.dll

to build the DLL.

Building the `DLL` from the IDE

Alternatively, the DLL can be build using Visual Studio as follows:

File -> New -> Project;
Installed -> Templates -> Visual C++ -> Windows -> Win32 -> Win32Project;
Next;
Application type -> DLL;
Additional options -> Empty project (select);
Additional options -> Precompiled header (unselect);
Project -> Properties -> Configuration Manager -> Active solution platform: x64;
Project -> Properties -> Configuration Manager -> Active solution configuration: Release.

Linking the DLL under Python

Under Python, do the following

import os
import sys
from ctypes import *

lib = cdll.LoadLibrary('testDLL.dll')

lib.testDLL(3)

User · Answer

ctypes can be used to access dlls  here s a tutorial   http   docs python org library ctypes html module-ctypes

User · Answer

This page has a very simple example of calling functions from a DLL file.

Paraphrasing the details here for completeness:

It's very easy to call a DLL function in Python. I have a self-made DLL file with two functions: add and sub which take two arguments.

add(a, b) returns addition of two numbers
sub(a, b) returns substraction of two numbers

The name of the DLL file will be "demo.dll"

Program:

from ctypes import*
# give location of dll
mydll = cdll.LoadLibrary("C:\\demo.dll")
result1= mydll.add(10,1)
result2= mydll.sub(10,1)
print "Addition value:"+result1
print "Substraction:"+result2

Output:

Addition value:11
Substraction:9

User · Answer

ctypes will be the easiest thing to use but (mis)using it makes Python subject to crashing. If you are trying to do something quickly, and you are careful, it's great.

I would encourage you to check out Boost Python. Yes, it requires that you write some C++ code and have a C++ compiler, but you don't actually need to learn C++ to use it, and you can get a free (as in beer) C++ compiler from Microsoft.

User · Answer

Maybe with Dispatch   from win32com client import Dispatch  zk   Dispatch  zkemkeeper ZKEM      Where zkemkeeper is a registered DLL file on the system    After that  you can access functions just by calling them   zk Connect Net IP address  port

User · Answer

Building a DLL and linking it under Python using ctypes

I present a fully worked example on how building a shared library and using it under Python by means of ctypes. I consider the Windows case and deal with DLLs. Two steps are needed:

Build the DLL using Visual Studio's compiler either from the command line or from the IDE;
Link the DLL under Python using ctypes.

The shared library

The shared library I consider is the following and is contained in the testDLL.cpp file. The only function testDLL just receives an int and prints it.

#include <stdio.h>
?
extern "C" {
?
__declspec(dllexport)
?
void testDLL(const int i) {
    printf("%d\n", i);
}
?
} // extern "C"

Building the DLL from the command line

To build a DLL with Visual Studio from the command line run

"C:\Program Files (x86)\Microsoft Visual Studio 12.0\Common7\Tools\vsdevcmd"

to set the include path and then run

cl.exe /D_USRDLL /D_WINDLL testDLL.cpp /MT /link /DLL /OUT:testDLL.dll

to build the DLL.

Building the `DLL` from the IDE

Alternatively, the DLL can be build using Visual Studio as follows:

File -> New -> Project;
Installed -> Templates -> Visual C++ -> Windows -> Win32 -> Win32Project;
Next;
Application type -> DLL;
Additional options -> Empty project (select);
Additional options -> Precompiled header (unselect);
Project -> Properties -> Configuration Manager -> Active solution platform: x64;
Project -> Properties -> Configuration Manager -> Active solution configuration: Release.

Linking the DLL under Python

Under Python, do the following

import os
import sys
from ctypes import *

lib = cdll.LoadLibrary('testDLL.dll')

lib.testDLL(3)

User · Answer

For ease of use  ctypes is the way to go   The following example of ctypes is from actual code I ve written  in Python 2 5    This has been  by far  the easiest way I ve found for doing what you ask   import ctypes    Load DLL into memory   hllDll   ctypes WinDLL   c   PComm  ehlapi32 dll      Set up prototype and parameters for the desired function call    HLLAPI  hllApiProto   ctypes WINFUNCTYPE       ctypes c int         Return type      ctypes c void p      Parameters 1         ctypes c void p      ctypes c void p      ctypes c void p          thru 4  hllApiParams    1   p1   0    1   p2   0    1   p3  0    1   p4  0      Actually map the call   HLLAPI        to a Python name   hllApi   hllApiProto    HLLAPI   hllDll   hllApiParams     This is how you can actually call the DLL function    Set up the variables and call the Python name with them   p1   ctypes c int  1  p2   ctypes c char p  sessionVar  p3   ctypes c int  1  p4   ctypes c int  0  hllApi  ctypes byref  p1   p2  ctypes byref  p3   ctypes byref  p4     The ctypes stuff has all the C-type data types  int  char  short  void   and so on  and can pass by value or reference   It can also return specific data types although my example doesn t do that  the HLL API returns values by modifying a variable passed by reference      In terms of the specific example shown above  IBM s EHLLAPI is a fairly consistent interface   All calls pass four void pointers  EHLLAPI sends the return code back through the fourth parameter  a pointer to an int so  while I specify int as the return type  I can safely ignore it  as per IBM s documentation here  In other words  the C variant of the function would be   int hllApi  void  p1  void  p2  void  p3  void  p4    This makes for a single  simple ctypes function able to do anything the EHLLAPI library provides  but it s likely that other libraries will need a separate ctypes function set up per library function   The return value from WINFUNCTYPE is a function prototype but you still have to set up more  parameter information  over and above the types   Each tuple in hllApiParams has a parameter  direction   1   input  2   output and so on   a parameter name and a default value - see the ctypes doco for details  Once you have the prototype and parameter information  you can create a Python  callable  hllApi with which to call the function  You simply create the needed variable  p1 through p4 in my case  and call the function with them

User · Answer

If the DLL is of type COM library  then you can use pythonnet   pip install pythonnet   Then in your python code  try the following  import clr clr AddReference  path to your dll      then instantiate an object as per the class in the DLL  and access the methods within it

User · Answer

If the DLL is of type COM library  then you can use pythonnet   pip install pythonnet   Then in your python code  try the following  import clr clr AddReference  path to your dll      then instantiate an object as per the class in the DLL  and access the methods within it

User · Answer

ctypes can be used to access dlls  here s a tutorial   http   docs python org library ctypes html module-ctypes

User · Answer

ctypes can be used to access dlls  here s a tutorial   http   docs python org library ctypes html module-ctypes

User · Answer

ctypes will be the easiest thing to use but (mis)using it makes Python subject to crashing. If you are trying to do something quickly, and you are careful, it's great.

I would encourage you to check out Boost Python. Yes, it requires that you write some C++ code and have a C++ compiler, but you don't actually need to learn C++ to use it, and you can get a free (as in beer) C++ compiler from Microsoft.

User · Answer

This page has a very simple example of calling functions from a DLL file.

Paraphrasing the details here for completeness:

It's very easy to call a DLL function in Python. I have a self-made DLL file with two functions: add and sub which take two arguments.

add(a, b) returns addition of two numbers
sub(a, b) returns substraction of two numbers

The name of the DLL file will be "demo.dll"

Program:

from ctypes import*
# give location of dll
mydll = cdll.LoadLibrary("C:\\demo.dll")
result1= mydll.add(10,1)
result2= mydll.sub(10,1)
print "Addition value:"+result1
print "Substraction:"+result2

Output:

Addition value:11
Substraction:9

User · Answer

Maybe with Dispatch   from win32com client import Dispatch  zk   Dispatch  zkemkeeper ZKEM      Where zkemkeeper is a registered DLL file on the system    After that  you can access functions just by calling them   zk Connect Net IP address  port

User · Answer

ctypes will be the easiest thing to use but (mis)using it makes Python subject to crashing. If you are trying to do something quickly, and you are careful, it's great.

I would encourage you to check out Boost Python. Yes, it requires that you write some C++ code and have a C++ compiler, but you don't actually need to learn C++ to use it, and you can get a free (as in beer) C++ compiler from Microsoft.

User · Answer

For ease of use  ctypes is the way to go   The following example of ctypes is from actual code I ve written  in Python 2 5    This has been  by far  the easiest way I ve found for doing what you ask   import ctypes    Load DLL into memory   hllDll   ctypes WinDLL   c   PComm  ehlapi32 dll      Set up prototype and parameters for the desired function call    HLLAPI  hllApiProto   ctypes WINFUNCTYPE       ctypes c int         Return type      ctypes c void p      Parameters 1         ctypes c void p      ctypes c void p      ctypes c void p          thru 4  hllApiParams    1   p1   0    1   p2   0    1   p3  0    1   p4  0      Actually map the call   HLLAPI        to a Python name   hllApi   hllApiProto    HLLAPI   hllDll   hllApiParams     This is how you can actually call the DLL function    Set up the variables and call the Python name with them   p1   ctypes c int  1  p2   ctypes c char p  sessionVar  p3   ctypes c int  1  p4   ctypes c int  0  hllApi  ctypes byref  p1   p2  ctypes byref  p3   ctypes byref  p4     The ctypes stuff has all the C-type data types  int  char  short  void   and so on  and can pass by value or reference   It can also return specific data types although my example doesn t do that  the HLL API returns values by modifying a variable passed by reference      In terms of the specific example shown above  IBM s EHLLAPI is a fairly consistent interface   All calls pass four void pointers  EHLLAPI sends the return code back through the fourth parameter  a pointer to an int so  while I specify int as the return type  I can safely ignore it  as per IBM s documentation here  In other words  the C variant of the function would be   int hllApi  void  p1  void  p2  void  p3  void  p4    This makes for a single  simple ctypes function able to do anything the EHLLAPI library provides  but it s likely that other libraries will need a separate ctypes function set up per library function   The return value from WINFUNCTYPE is a function prototype but you still have to set up more  parameter information  over and above the types   Each tuple in hllApiParams has a parameter  direction   1   input  2   output and so on   a parameter name and a default value - see the ctypes doco for details  Once you have the prototype and parameter information  you can create a Python  callable  hllApi with which to call the function  You simply create the needed variable  p1 through p4 in my case  and call the function with them

User · Answer

For ease of use  ctypes is the way to go   The following example of ctypes is from actual code I ve written  in Python 2 5    This has been  by far  the easiest way I ve found for doing what you ask   import ctypes    Load DLL into memory   hllDll   ctypes WinDLL   c   PComm  ehlapi32 dll      Set up prototype and parameters for the desired function call    HLLAPI  hllApiProto   ctypes WINFUNCTYPE       ctypes c int         Return type      ctypes c void p      Parameters 1         ctypes c void p      ctypes c void p      ctypes c void p          thru 4  hllApiParams    1   p1   0    1   p2   0    1   p3  0    1   p4  0      Actually map the call   HLLAPI        to a Python name   hllApi   hllApiProto    HLLAPI   hllDll   hllApiParams     This is how you can actually call the DLL function    Set up the variables and call the Python name with them   p1   ctypes c int  1  p2   ctypes c char p  sessionVar  p3   ctypes c int  1  p4   ctypes c int  0  hllApi  ctypes byref  p1   p2  ctypes byref  p3   ctypes byref  p4     The ctypes stuff has all the C-type data types  int  char  short  void   and so on  and can pass by value or reference   It can also return specific data types although my example doesn t do that  the HLL API returns values by modifying a variable passed by reference      In terms of the specific example shown above  IBM s EHLLAPI is a fairly consistent interface   All calls pass four void pointers  EHLLAPI sends the return code back through the fourth parameter  a pointer to an int so  while I specify int as the return type  I can safely ignore it  as per IBM s documentation here  In other words  the C variant of the function would be   int hllApi  void  p1  void  p2  void  p3  void  p4    This makes for a single  simple ctypes function able to do anything the EHLLAPI library provides  but it s likely that other libraries will need a separate ctypes function set up per library function   The return value from WINFUNCTYPE is a function prototype but you still have to set up more  parameter information  over and above the types   Each tuple in hllApiParams has a parameter  direction   1   input  2   output and so on   a parameter name and a default value - see the ctypes doco for details  Once you have the prototype and parameter information  you can create a Python  callable  hllApi with which to call the function  You simply create the needed variable  p1 through p4 in my case  and call the function with them

User · Answer

For ease of use  ctypes is the way to go   The following example of ctypes is from actual code I ve written  in Python 2 5    This has been  by far  the easiest way I ve found for doing what you ask   import ctypes    Load DLL into memory   hllDll   ctypes WinDLL   c   PComm  ehlapi32 dll      Set up prototype and parameters for the desired function call    HLLAPI  hllApiProto   ctypes WINFUNCTYPE       ctypes c int         Return type      ctypes c void p      Parameters 1         ctypes c void p      ctypes c void p      ctypes c void p          thru 4  hllApiParams    1   p1   0    1   p2   0    1   p3  0    1   p4  0      Actually map the call   HLLAPI        to a Python name   hllApi   hllApiProto    HLLAPI   hllDll   hllApiParams     This is how you can actually call the DLL function    Set up the variables and call the Python name with them   p1   ctypes c int  1  p2   ctypes c char p  sessionVar  p3   ctypes c int  1  p4   ctypes c int  0  hllApi  ctypes byref  p1   p2  ctypes byref  p3   ctypes byref  p4     The ctypes stuff has all the C-type data types  int  char  short  void   and so on  and can pass by value or reference   It can also return specific data types although my example doesn t do that  the HLL API returns values by modifying a variable passed by reference      In terms of the specific example shown above  IBM s EHLLAPI is a fairly consistent interface   All calls pass four void pointers  EHLLAPI sends the return code back through the fourth parameter  a pointer to an int so  while I specify int as the return type  I can safely ignore it  as per IBM s documentation here  In other words  the C variant of the function would be   int hllApi  void  p1  void  p2  void  p3  void  p4    This makes for a single  simple ctypes function able to do anything the EHLLAPI library provides  but it s likely that other libraries will need a separate ctypes function set up per library function   The return value from WINFUNCTYPE is a function prototype but you still have to set up more  parameter information  over and above the types   Each tuple in hllApiParams has a parameter  direction   1   input  2   output and so on   a parameter name and a default value - see the ctypes doco for details  Once you have the prototype and parameter information  you can create a Python  callable  hllApi with which to call the function  You simply create the needed variable  p1 through p4 in my case  and call the function with them

User · Answer

ctypes can be used to access dlls  here s a tutorial   http   docs python org library ctypes html module-ctypes

User · Answer

ctypes will be the easiest thing to use but (mis)using it makes Python subject to crashing. If you are trying to do something quickly, and you are careful, it's great.

I would encourage you to check out Boost Python. Yes, it requires that you write some C++ code and have a C++ compiler, but you don't actually need to learn C++ to use it, and you can get a free (as in beer) C++ compiler from Microsoft.

[python] How can I use a DLL file from Python?

The answer is

Building a DLL and linking it under Python using ctypes

The shared library

Building the DLL from the command line

Building the `DLL` from the IDE

Linking the DLL under Python

Building a DLL and linking it under Python using ctypes

The shared library

Building the DLL from the command line

Building the `DLL` from the IDE

Linking the DLL under Python

Examples related to python

Examples related to dll

Tags

[python] How can I use a DLL file from Python?

The answer is

Building a DLL and linking it under Python using ctypes

The shared library

Building the DLL from the command line

Building the DLL from the IDE

Linking the DLL under Python

Building a DLL and linking it under Python using ctypes

The shared library

Building the DLL from the command line

Building the DLL from the IDE

Linking the DLL under Python

Examples related to python

Examples related to dll

Tags

Building the `DLL` from the IDE

Building the `DLL` from the IDE