Python ctypes dll call

Question

So I am basically new to python ctypes and I have little or no knowledge on C programming or any none python language...but I have a solid understanding of the dll protocol and working...so I made this call into a dll file to access a printf and then use it....my result came out oddly and not as expected....can anyone help explain what is happening here ...here's my code

From ctypes import *

msvcrt = cdll.msvcrt
message_string = "Hello World! \n"
msvcrt.printf("Testing: %s", message_string)

And here is my result

zvi · Answer 1 · 2020-09-06T18:56:25.803

0

The reason is that you must pass a bytes string (b"whatever") not a regular python literal string.

https://stackoverflow.com/a/6273618/3870025

From ctypes import *
msvcrt = cdll.msvcrt
message_string = "Hello World! \n"
msvcrt.printf(b"Testing: %s", message_string)

edited Sep 06 '20 at 18:56

answered Sep 06 '20 at 18:38

zvi

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You might have forgotten the `b` before the string to make it type byte. – aerijman Sep 06 '20 at 18:44

score 0 · Answer 2 · answered Nov 22 '20 at 03:14

from ctypes import *
msvcrt = cdll.msvcrt

message_string = b"Hello World!\n"
msvcrt.printf(b"Testing: %s", message_string)

Note that printf prints to the real standard output channel, not to sys.stdout, so these examples will only work at the console prompt, not from within IDLE or PythonWin:

Python ctypes dll call

2 Answers2