Question

在为getmntent linux libc函数编写python包装器时，以下代码在python 2.x和3.x之间的行为存在奇怪的区别，其中大部分实际工作是由C库完成的。由于我经常将C代码与python接口，因此谁能解释或纠正出了什么问题？

import ctypes
import sys

class mntent(ctypes.Structure):
    _fields_ = [("fsname", ctypes.c_char_p),
                ("dir", ctypes.c_char_p),
                ("type", ctypes.c_char_p),
                ("opts", ctypes.c_char_p),
                ("freq", ctypes.c_int),
                ("passno", ctypes.c_int)]

def main():
    libc = ctypes.cdll.LoadLibrary('libc.so.6')
    libc.getmntent.restype = ctypes.POINTER(mntent)
    libc.fopen.restype = ctypes.POINTER(ctypes.c_void_p)
    fp = libc.fopen('/etc/mtab', 'r')
    while True:
        mounts = libc.getmntent(fp)
        if bool(mounts) == False:
            libc.fclose(fp)
            break
        print("%30s   %10s    %s"%(mounts.contents.dir, mounts.contents.type, mounts.contents.fsname))

main()

预期输出包含列出的所有安装设备及其类型和安装点。在python 3.x上，它提供了一个空列表。

Answer 1

在Python 3中，所有字符串都是unicode，但是import numpy as np import cv2 import cv2.aruco as aruco import glob import math markerLength = 0.25 cap = cv2.VideoCapture(0) criteria = (cv2.TERM_CRITERIA_EPS + cv2.TERM_CRITERIA_MAX_ITER, 30, 0.001) objp = np.zeros((6*7,3), np.float32) objp[:,:2] = np.mgrid[0:7,0:6].T.reshape(-1,2) objpoints = [] imgpoints = [] images = glob.glob('calib_images/*.jpg') for fname in images: img = cv2.imread(fname) gray = cv2.cvtColor(img,cv2.COLOR_BGR2GRAY) ret, corners = cv2.findChessboardCorners(gray, (7,6),None) if ret == True: objpoints.append(objp) corners2 = cv2.cornerSubPix(gray,corners,(11,11),(-1,-1),criteria) imgpoints.append(corners2) img = cv2.drawChessboardCorners(img, (7,6), corners2,ret) ret, mtx, dist, rvecs, tvecs = cv2.calibrateCamera(objpoints, imgpoints, gray.shape[::-1],None,None) calibrationFile = "calibrationFileName.xml" calibrationParams = cv2.FileStorage(calibrationFile, cv2.FILE_STORAGE_READ) camera_matrix = calibrationParams.getNode("cameraMatrix").mat() dist_coeffs = calibrationParams.getNode("distCoeffs").mat() count = 1 while(True): ret, frame = cap.read() gray = cv2.cvtColor(frame, cv2.COLOR_BGR2GRAY) aruco_dict = aruco.Dictionary_get(aruco.DICT_6X6_250) arucoParameters = aruco.DetectorParameters_create() aruco_list = {} corners, ids, rejectedImgPoints = aruco.detectMarkers(gray, aruco_dict, parameters=arucoParameters) if np.all(ids != None): if len(corners): for k in range(len(corners)): temp_1 = corners[k] temp_1 = temp_1[0] temp_2 = ids[k] temp_2 = temp_2[0] aruco_list[temp_2] = temp_1 key_list = aruco_list.keys() font = cv2.FONT_HERSHEY_SIMPLEX for key in key_list: dict_entry = aruco_list[key] centre = dict_entry[0] + dict_entry[1] + dict_entry[2] + dict_entry[3] centre[:] = [int(x / 4) for x in centre] orient_centre = centre + [0.0,5.0] centre = tuple(centre) orient_centre = tuple((dict_entry[0]+dict_entry[1])/2) cv2.circle(frame,centre,1,(0,0,255),8) display = aruco.drawDetectedMarkers(frame, corners) display = np.array(display) else: display = frame cv2.imshow('Display',display) if cv2.waitKey(1) & 0xFF == ord('q'): break cap.release() cv2.destroyAllWindows()希望简单字节字符串作为其参数：

libc.fopen()

Ctypes Linux行为在py2和py3上有所不同

1 个答案: