Python3类型错误：一个字节样的对象是必需的，而不是str

Question

我正在尝试遵循这个OpenCV练习http://coding-robin.de/2013/07/22/train-your-own-opencv-haar-classifier.html 但是在运行mergevec.py的步骤中遇到了困难（我使用Python版本而不是.cpp版本）。我使用的是Python3，而不是本文中提到的Python2.x。

此文件的源是https://github.com/wulfebw/mergevec/blob/master/mergevec.py

我得到的错误是

Traceback (most recent call last):
  File "./tools/mergevec1.py", line 96, in <module>
    merge_vec_files(vec_directory, output_filename)
  File "./tools/mergevec1.py", line 45, in merge_vec_files
    val = struct.unpack('<iihh', content[:12])
TypeError: a bytes-like object is required, not 'str'

我试着遵循python 3.5:TypeError：在写入文件时需要一个类似字节的对象，而不是'str'，并使用open（f，'r'，encoding='utf-8'，errors='ignore'）。

我修改的代码如下：

import sys
import glob
import struct
import argparse
import traceback


def exception_response(e):
    exc_type, exc_value, exc_traceback = sys.exc_info()
    lines = traceback.format_exception(exc_type, exc_value, exc_traceback)
    for line in lines:
        print(line)

def get_args():
    parser = argparse.ArgumentParser()
    parser.add_argument('-v', dest='vec_directory')
    parser.add_argument('-o', dest='output_filename')
    args = parser.parse_args()
    return (args.vec_directory, args.output_filename)

def merge_vec_files(vec_directory, output_vec_file):


    # Check that the .vec directory does not end in '/' and if it does, remove it.
    if vec_directory.endswith('/'):
        vec_directory = vec_directory[:-1]
    # Get .vec files
    files = glob.glob('{0}/*.vec'.format(vec_directory))

    # Check to make sure there are .vec files in the directory
    if len(files) <= 0:
        print('Vec files to be mereged could not be found from directory: {0}'.format(vec_directory))
        sys.exit(1)
    # Check to make sure there are more than one .vec files
    if len(files) == 1:
        print('Only 1 vec file was found in directory: {0}. Cannot merge a single file.'.format(vec_directory))
        sys.exit(1)


    # Get the value for the first image size
    prev_image_size = 0
    try:
        with open(files[0], 'r', encoding='utf-8', errors='ignore') as vecfile:
            content = ''.join(str(line) for line in vecfile.readlines())
            val = struct.unpack('<iihh', content[:12])
            prev_image_size = val[1]
    except IOError as e:
        f = None
        print('An IO error occured while processing the file: {0}'.format(f))
        exception_response(e)


    # Get the total number of images
    total_num_images = 0
    for f in files:
        try:
            with open(f, 'r', encoding='utf-8', errors='ignore') as vecfile:
                content = ''.join(str(line) for line in vecfile.readlines())
                val = struct.unpack('<iihh', content[:12])
                num_images = val[0]
                image_size = val[1]
                if image_size != prev_image_size:
                    err_msg = """The image sizes in the .vec files differ. These values must be the same. \n The image size of file {0}: {1}\n 
                        The image size of previous files: {0}""".format(f, image_size, prev_image_size)
                    sys.exit(err_msg)

                total_num_images += num_images
        except IOError as e:
            print('An IO error occured while processing the file: {0}'.format(f))
            exception_response(e)


    # Iterate through the .vec files, writing their data (not the header) to the output file
    # '<iihh' means 'little endian, int, int, short, short'
    header = struct.pack('<iihh', total_num_images, image_size, 0, 0)
    try:
        with open(output_vec_file, 'wb') as outputfile:
            outputfile.write(header)

            for f in files:
                with open(f, 'w', encoding='utf-8', errors='ignore') as vecfile:
                    content = ''.join(str(line) for line in vecfile.readlines())
                    data = content[12:]
                    outputfile.write(data)
    except Exception as e:
        exception_response(e)


if __name__ == '__main__':
    vec_directory, output_filename = get_args()
    if not vec_directory:
        sys.exit('mergvec requires a directory of vec files. Call mergevec.py with -v /your_vec_directory')
    if not output_filename:
        sys.exit('mergevec requires an output filename. Call mergevec.py with -o your_output_filename')

    merge_vec_files(vec_directory, output_filename)

你知道我做错了什么吗？谢谢。

更新1

我这样做：

content = b''.join(str(line) for line in vecfile.readlines())

我基本上在前面加了“b”。但是，现在我得到了一个不同的错误：

回溯（最后一次调用）：文件“/tools/mergevec1.py”，第97行，在merge\u-vec\u文件（vec\u目录，输出文件名）文件“/tools/mergevec1.py”，第44行，在merge\u-vec\u-files-content=b.”中。join（str（line）表示vecfile.readlines（）中的行）类型错误：序列项0：应为类似对象的字节，str-find

Answer 1

当我改变它时，我能够解决我的问题：

for f in files:
            with open(f, 'rb') as vecfile:
                content = ''.join(str(line) for line in vecfile.readlines())
                data = content[12:]
                outputfile.write(data)
except Exception as e:
    exception_response(e)

对于it：

for f in files:
            with open(f, 'rb') as vecfile:
                content = b''.join((line) for line in vecfile.readlines())
                outputfile.write(bytearray(content[12:]))
except Exception as e:
    exception_response(e)

就像我改变它之前一样：

content = ''.join(str(line) for line in vecfile.readlines())

对于it：

content = b''.join((line) for line in vecfile.readlines())

因为它在等待一些str，现在它能够接收我们需要的二进制档案。

您保留错误是因为您正在使用代码

content = b''.join(str(line) for line in vecfile.readlines())

您必须使用：

content = b''.join((line) for line in vecfile.readlines())

这是没有“str”演员阵容的。

Answer 2

正如OP所解释的，文件包含二进制数据。为了处理二进制数据：

1. 文件应以二进制模式打开，方法是使用'rb'作为open调用中的模式

对于问题中提供的代码，用于读取图像的代码部分应为：

for f in files:
    try:
        with open(f, 'rb') as vecfile:
            content = vecfile.read()
            val = struct.unpack('<iihh', content[:12])
            num_images = val[0]
            image_size = val[1]
            if image_size != prev_image_size:
                err_msg = """The image sizes in the .vec files differ. These values must be the same. \n The image size of file {0}: {1}\n 
                    The image size of previous files: {0}""".format(f, image_size, prev_image_size)
                sys.exit(err_msg)

            total_num_images += num_images
    except IOError as e:
        print('An IO error occured while processing the file: {0}'.format(f))
        exception_response(e)