如何使用sqlite3作为回调函数所需的python函数的ctypes进行编码和换行？

我正在尝试从python执行 sqlite3_exec 以逐行提取数据库的内容。根据 C API ，我需要一个回调函数来执行迭代。我在互联网上提供了许多帮助，对以下代码进行了编码：

I'm trying to perform sqlite3_exec from python to extract line by line the contents of a database. According to the C API, I need a Callback function which will perform the iteration. I have coded the following with a lot of help from internet:

已使用@eryksun建议进行了更新

import ctypes

def extractor(unused, num_columns, pcolumn, pcolumn_name):
    for column in range(0,num_columns):
        if pcolumn[i] != None:
            print pcolumn[i]

sqlite3DLL = ctypes.CDLL("C:\\Python\\PYTHON\\DLLs\\sqlite3.dll")
SQLITE_OPEN_READONLY = 1 
null_ptr = ctypes.c_void_p(None)
p_src_db = ctypes.c_void_p(None)

ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_void_p, ctypes.POINTER(ctypes.c_char_p), ctypes.POINTER(ctypes.c_char_p))
callback_func = callback_type(extractor)

connect = sqlite3DLL.sqlite3_open_v2(DatabasePath, ctypes.byref(p_src_db), SQLITE_OPEN_READONLY, null_ptr)
connect = sqlite3DLL.sqlite3_exec(DatabasePath, "SELECT * FROM *", callback_func, None, null_ptr)
sqlite3DLL.sqlite3_close(DatabasePath)

在继续使用python回调函数之前，我有一些疑问：

Before moving on to the python callback function I have some doubts:

1. SELECT * FROM * 是否可能是 SQL语句，以避免提供表名（因为我不知道它的名字）


2. 两个函数的第一个参数 sqlite3_open_v2 和 sqlite3_exec 是数据库的路径？

1. Is "SELECT * FROM *" a possible SQL statement to avoid providing the name of a table (because I do not know it)?
2. Is the first argument of both functions sqlite3_open_v2 and sqlite3_exec the path to the database?

如果一切正常，我们可以继续使用回调函数。根据我在网上发现的内容，C回调函数应与以下类似：

If all that is ok we can move on to the callback function. According to what I found on the net, the C callback function should be somewhat similar to:

callback(void *NotUsed, int argc, char **argv, char **azColName)
    for (int i = 0; i < argc; i++) {printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL")}

这就是为什么我将 CFUNCTYPE 。我该如何编码与可能用数据库内容填充列表的回调函数相匹配的python函数？

That is why I coded the CFUNCTYPE you see on my code. How can I code a python function which matches the callback needed to maybe fill a list with the database contents?

我已在代码中添加了建议的更改，即回调函数只是打印该值以验证输出。但这无法正常工作，但我得到一个错误：

I have added the proposed changes on the code, the callback function just prints the value to verify the output. But It wont work I get an error:

con = sqlite3DLL.sqlite3_exec(FastenerLibraryPath, "SELECT * FROM *", callback_func, None, null_ptr)
WindowsError: exception: access violation writing 0x0000000000000009

非常感谢！

最终版本（@eryksun注释和@MarkTolonen解决方案）

import ctypes

def extractor(unused, num_columns, pcolumn, pcolumn_name):
    print ','.join(["''" if x is None else "'"+x+"'" for x in pcolumn[:num_columns]])
    return 0

sqlite3DLL = ctypes.CDLL("C:\\Python\\PYTHON\\DLLs\\sqlite3.dll")
SQLITE_OPEN_READONLY = 1 
null_ptr = ctypes.c_void_p(None)
p_src_db = ctypes.c_void_p(None)

ctypes.CFUNCTYPE(ctypes.CFUNCTYPE(ctypes.c_int, ctypes.c_void_p, ctypes.c_int, ctypes.POINTER(ctypes.c_char_p), ctypes.POINTER(ctypes.c_char_p))
callback_func = callback_type(extractor)

connect = sqlite3DLL.sqlite3_open_v2(DatabasePath, ctypes.byref(p_src_db), SQLITE_OPEN_READONLY, None)
connect = sqlite3DLL.sqlite3_exec(p_src_db, b"SELECT * FROM Pin", callback_func, None, None)
sqlite3DLL.sqlite3_close(p_src_db)

这是可行的，我将研究 argtypes 和不透明类型。

This is working, however, I will look into argtypes and the opaque type.

谢谢大家！