在Python中使用回调时出错 [英] Error using callback in Python
问题描述
我正在开发一个应该在Python中使用的dll。我有一个回调函数发送我的参数（在一个单独的标题中定义）：
typedef int（* call_nBest）因此，我以这种方式使用这个回调函数：
#define TEXT_BUFFER_MAX_SIZE 50
call_nBest nBestList;
void Xfunction（const char * aLineThatWillBeConvertedInAList）{
char ** results;
float * confidences;
confidences = new float [nBest];
results = new char * [nBest];
for（int i = 0; i
MakeLine2List（aLineThatWillBeConvertedInAList，results，confidences）;
/ *在这个函数我有错误：（* /
nBestList（results，confidences，nBest）; //将值传递给我的回调
for（int i = 0; i
delete [] results;
}
我以这种方式导出：
__ declspec（dllexport）int ResultCallback（call_nBest theList）{
nBestList = theList;
return（0）;
}
我以这种方式在另一个C ++应用程序中测试了我的回调：
int MyCallback（char ** OutLi，float * confLi，int nB）{
printf（\\\
nB results：％d \\\
，nB） ;
for（int n = 0; n
}
return（0）;
}
在 main（）我以这种方式给回调：
ResultCallback（MyCallback）;
但我不知道如何适应这个Python。我尝试过：
注意：我改变了最后一种方式，因为我解决了一些错误， 。这是目前的方式，我如何加载 myDLL
从ctypes import bb
def callbackU（outList，ConList，nB）：
for i in range（nB）：
print（OutList [i] [0:50]）＃如何打印值
return 0
myDLL = cdll.LoadLibrary（MyLibrary.dll）
calling = CFUNCTYPE（c_int，POINTER ）），POINTER（c_float），c_int）
theCall = calling（callbackU）
myDLL.ResultCallback（theCall）
myDLL.StartProcess ＃在此过程中，给定的回调将被调用
ERROR
现在我有这个错误：
未处理的异常：System.AccessViolationException：尝试
问题签名：
读或写保护内存。这通常表明其他
内存已损坏。
问题事件名称：APPCRASH < br>
应用程序名称：python.exe
应用程序版本：0.0.0.0
应用程序时间戳：54f9ed12
故障模块名称：MSVCR100.dll
故障模块版本：10.0.40219.325
故障模块时间戳记：10.0.40219.325
异常代码：c0000005
异常偏移：00001ed7
操作系统版本：6.3.9600.2.0.0.256.4
语言ID：1033
其他信息1：5861
其他信息2 ：5861822e1919d7c014bb064c64908b2
其他信息3：a10f
其他信息4：a10ff7d2bb2516fdc753f9c34fc3b069
我已经做了，几乎是我想要的：
首先我改变了这个回调Python函数：
def callbackU（OutList，ConList，nB）：
for i in range（nB）：
print（i）
return 0
所有工作没有错误，我可以在控制台中看到这个（在这种情况下 nB 为 10 ）：
0
1
...
9
函数如下：
def callbackU（OutList，ConList，nB）：
for i in range ）：
print（cast（outList，c_char_p））
return 0
（nB次）
你想要这样的东西吗？ / p>
def callbackU（OutList，ConList，nB）：
for i in range（nB）：
print （{} \t {}。格式（ConList [i]，cast（outList [i]，c_char_p）））
return 0
从我的理解你只是试图匹配Python callbackU 函数的输出与您的C ++ MyCallback 函数。
Python有各种各样的字符串格式化功能，可以先混淆，但支持 printf 字符串格式化。
由于 OutList 有类型 LP_LP_c_char （指向 c_char ，vsNULL terminated char * c_char_p ），我们最好将其转换为本地Python数据类型如下：
def callbackU（OutList，ConList，nB）：
for i in range ）：
out_list_item = cast（outList [i]，c_char_p）.value
print（{} \t {}。format（ConList [i]，out_list_item））
return 0
I am developing a dll that should be used in Python. I have a callback function to send my parameters (defined in a separate header):
typedef int(*call_nBest)(char **OutList, float* confList, int nB);
So, I'm using this callback in this way:
#define TEXT_BUFFER_MAX_SIZE 50
call_nBest nBestList;
void Xfunction(const char* aLineThatWillBeConvertedInAList){
char **results;
float *confidences;
confidences=new float[nBest];
results=new char*[nBest];
for(int i=0; i<nBest; i++) results[i]=new char[TEXT_BUFFER_MAX_SIZE];
MakeLine2List(aLineThatWillBeConvertedInAList,results,confidences);
/*At this function I am having the error :(*/
nBestList(results,confidences,nBest); // Passing the values to my callback
for(int i=0; i<nBest; i++) delete [] results[i];
delete [] confidences;
delete [] results;
}
And I'm exporting it in this way:
__declspec(dllexport) int ResultCallback(call_nBest theList){
nBestList = theList;
return(0);
}
I tested my callback first in another C++ application in this way:
int MyCallback(char **OutLi, float* confLi, int nB){
printf("\n The nB results: %d \n",nB);
for(int n=0; n<nB; n++){
std::cout << *(confLi+n) << "\t" << OutLi[n] << "\n";
}
return(0);
}
In main() I give the callback in this way:
ResultCallback(MyCallback);
and it works pretty well. But I don't have any idea how to adapt this to Python. I have tried this:
Note: I have changed the last way, because I resolved some mistakes, but I'm still getting an error. This is the current way of how I am loading myDLL
from ctypes import *
def callbackU(OutList,ConList,nB):
for i in range(nB):
print(OutList[i][0:50]) #I don't know how to print the values
return 0
myDLL = cdll.LoadLibrary("MyLibrary.dll")
calling = CFUNCTYPE(c_int,POINTER(POINTER(c_char)),POINTER(c_float),c_int)
theCall= calling(callbackU)
myDLL.ResultCallback(theCall)
myDLL.StartProcess(); #In this process the given callback will be invoqued
ERROR
And now I have this error:
Unhandled Exception: System.AccessViolationException: Attempted to read or write protected memory. This is often an indication that other memory is corrupt. at Xfunction(SByte* aLineThatWillBeConvertedInAList)
Problem signature:
Problem Event Name: APPCRASH
Application Name: python.exe
Application Version: 0.0.0.0
Application Timestamp: 54f9ed12
Fault Module Name: MSVCR100.dll
Fault Module Version: 10.0.40219.325
Fault Module Timestamp: 10.0.40219.325
Exception Code: c0000005
Exception Offset: 00001ed7
OS Version: 6.3.9600.2.0.0.256.4
Locale ID: 1033
Additional Information 1: 5861
Additional Information 2: 5861822e1919d7c014bbb064c64908b2
Additional Information 3: a10f
Additional Information 4: a10ff7d2bb2516fdc753f9c34fc3b069
Things that I've done and are almost what I want:
First I changed the callback Python function for this one:
def callbackU(OutList,ConList,nB):
for i in range(nB):
print(i)
return 0
All works with no error and I can see this in the Console (in this case nB was 10):
0
1
...
9
Second, I changed the function as this one:
def callbackU(OutList,ConList,nB):
for i in range(nB):
print (cast(OutList,c_char_p))
return 0
and, oh surprise this prints only the first word of the list (nB times)
Do you want something like this?
def callbackU(OutList, ConList, nB):
for i in range(nB):
print("{}\t{}".format(ConList[i], cast(OutList[i], c_char_p)))
return 0
From what I understand you're just trying to match the output of your Python callbackU function with your C++ MyCallback function.
Python has a variety of string formatting functionality that can be confusing at first, but pays homage to printf string formatting.
Since OutList has type LP_LP_c_char (pointer to pointer of c_char, vs "NULL terminated char *" c_char_p), we'd best turn it into a native Python data type like so:
def callbackU(OutList, ConList, nB):
for i in range(nB):
out_list_item = cast(OutList[i], c_char_p).value
print("{}\t{}".format(ConList[i], out_list_item))
return 0
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