Question

Short version:
How can I get the address that a ctypes pointer points to?

Long version:
I have registered a python function as a callback with a C library. The C library expects function signature of void (*p_func)(char stat, char * buf, short buf_len) so I register an appropriate python function. When I get into the python function, I want to know the memory address pointed to by buf. How can I do this?

Answer 1

I have fixed this myself by reading the documentation.

I wanted to know the memory location of a block of memory allocated by a library. I had the ctypes pointer that pointed to said block. To get the memory address of the block I used ctypes.addressof(p_block.contents).

The confusion arose around my understanding that p_block.contents != p_block.contents, but then I realised all p_block.contents objects have the same underlying buffer. The address of the underlying buffer is obtained with ctypes.addressof.