PycURL上传含非ASCII字符路径文件报error 26问题求助

• Windows 10 操作系统
• Python 3.10.4
• PycURL 7.45.1

需要通过HTTP POST请求向指定API接口上传本地文件，但本地文件完整路径包含德语变音符号（Umlauts，例如字符ö，位于系统用户名路径段），示例文件路径为："C:\\Users\\NameWith_ö\\folder\\another_folder\\more_folders\\file.pdf"。
已知PycURL仅支持纯ASCII字符串或字节串类型传入参数，因此预先实现编码逻辑，将所有传入PycURL的字符串参数编码为UTF-8格式字节串。该操作解决了此前调用curl.setopt(curl.HTTPPOST, files)时抛出的UnicodeEncodeError异常，但路径编码为UTF-8字节串后，请求执行时抛出(error 26, '')错误，无法完成文件上传。

POST请求核心方法 #

def post(self, request_url, custom_headers : list = None, upload_fields : dict = None, upload_files : dict = None, further_directives : dict = None, proxy : dict = None):
        """
        Posts a HTTP POST request and returns a response object.

        :param request_url: The URL that request should point to.
        :type request_url: string
        :param custom_headers: An optional list of costum headers that should be sent with the request.
        :type custom_headers: list
        :param upload_fields: An optional dict of data that should be inputted into targeted upload fields {key = field name: value = input data}.
        :type upload_fields: dict
        :param upload_files: An optional dict of files that should be uploaded to the target site {key = field name: value = dict {key = 'filepath': value = path to file (required), key = 'new_filename': value = new name for uploaded file (optional), key = 'content_type': value = content type (optional, default is 'multipart/form-data')}}.
        :type upload_files: dict
        :param further_directives: An optional dict of further directives that should be included in the request (for list of all possible directives see PLACEHOLDER).
        :type further_directives: dict
        :param proxy: An optional dict of information used to route the request through a proxy {key = proxy port: value = int, key = proxy domain: value = string}
        :type proxy: dict

        :returns: Response object.
        :rtype: Curlified_Response
        """

        self.prepare_new_request()

        body_buffer = BytesIO()
        curl = pycurl.Curl()

        request_url, custom_headers, further_directives, proxy, upload_fields, upload_files = self.encode_strings(request_url, custom_headers, further_directives, proxy, upload_fields, upload_files)

        curl.setopt(curl.URL, request_url)
        if proxy:
            self.inject_kerberos_proxy(proxy['proxy port'], proxy['proxy domain'], curl)#
        if custom_headers:
            curl.setopt(curl.HTTPHEADER, custom_headers)#
        if further_directives:
            for item in further_directives.items():
                self.include_further_directive(item, curl)#
        if upload_fields:
            postfields = urlencode(upload_fields)#
            curl.setopt(curl.POSTFIELDS, postfields)
        if upload_files:
            files = []
            for item in upload_files.items():
                files.append(self.build_file_upload(item, curl))#
            curl.setopt(curl.HTTPPOST, files)
        curl.setopt(curl.HEADERFUNCTION, self.read_header_line)
        curl.setopt(curl.WRITEFUNCTION, body_buffer.write)
        curl.perform()
        self.read_body(body_buffer)
        curl.close()

文件上传表单项构建方法build_file_upload #

def build_file_upload(self, item, curl):
        """
        Gets a tuple of information for a file upload, checks the correctnes of the content and returns the properly built input.
        """

        info_list = []
        for i in item[1].items():
            if i[0] == 'filepath':
                info_list.append(curl.FORM_FILE)
                info_list.append(i[1])
            elif i[0] == 'new filename':
                info_list.append(curl.FORM_FILENAME)
                info_list.append(i[1])
            elif i[0] == 'contenttype':
                info_list.append(curl.FORM_CONTENTTYPE)
                info_list.append(i[1])
            else:
                raise ArgumentsError("No known file upload key was provided! Please revise.")
        if not info_list:
            raise RequiredArgumentsMissing("One or more required parameters for the file to be uploaded are missing! Please revise.")
        if 'content_type' not in info_list:
            info_list.append(curl.FORM_CONTENTTYPE)
            info_list.append(b'multipart/form-data')
        return (item[0], tuple(info_list))

字符串编码方法encode_strings #

def encode_strings(self, request_url, custom_headers, further_directives, proxy, upload_fields = None, upload_files = None):
        """
        Turns all given strings into bytes to be processable by PycURL.
        """

        custom_headers = [] if custom_headers is None else custom_headers
        upload_fields = {} if upload_fields is None else upload_fields
        upload_files = {} if upload_files is None else upload_files
        further_directives = {} if further_directives is None else further_directives
        proxy = {} if proxy is None else proxy

        request_url = bytes(request_url, 'UTF-8')
        for i in range(len(custom_headers)):
            if isinstance(custom_headers[i], str):
                custom_headers[i] = bytes(custom_headers[i], 'UTF-8')
        for k, v in further_directives.items():
            if isinstance(v, str):
                further_directives[k] = bytes(further_directives[k], 'UTF-8')
        for k, v in proxy.items():
            if isinstance(v, str):
                proxy[k] = bytes(proxy[k], 'UTF-8')
        for k, v in upload_fields.items():
            if isinstance(v, str):
                upload_fields[k] = bytes(upload_fields[k], 'UTF-8')
        for k, v in upload_files.items():
            if isinstance(v, dict):
                for key, value in v.items():
                    if isinstance(value, str):
                        upload_files[k][key] = bytes(upload_files[k][key], 'UTF-8')
        
        if len(upload_fields) == 0 and len(upload_files) == 0:
            return request_url, custom_headers, further_directives, proxy
        else:
            return request_url, custom_headers, further_directives, proxy, upload_fields, upload_files

PycURL抛出的error 26对应libcurl的CURLE_READ_ERROR错误，本质是底层libcurl无法读取指定路径的文件。
问题出在文件路径的编码逻辑上：Windows系统原生使用UTF-16（宽字符）编码处理文件路径，当前版本PycURL绑定的libcurl在Windows平台不会自动将传入的UTF-8字节路径转换为系统兼容的宽字符路径，直接传入UTF-8编码的带非ASCII字符（如德语变音ö）的路径时，系统无法定位到对应文件，最终触发读文件错误。
之前将所有字符串统一转UTF-8字节的逻辑，只解决了PycURL接口本身不接受Unicode字符串的参数校验问题，没有解决Windows平台文件路径的编码兼容问题。

优先选择手动读取文件内容传入的方案，绕开libcurl的路径解析逻辑，兼容性最好：

1. 修改encode_strings方法，跳过对upload_files中filepath字段的编码转换，保留原生Python字符串类型，交给Python内置的文件IO处理。Python 3在Windows下会自动调用系统宽字符API打开文件，完美支持带任意Unicode字符的路径。
2. 改造build_file_upload方法的filepath分支，不直接传路径给libcurl，而是手动打开文件读取内容，通过FORM_BUFFER系列参数传入：

import os
if i[0] == 'filepath':
    # 用Python原生方法打开文件，自动适配系统路径编码
    with open(i[1], 'rb') as f:
        file_content = f.read()
    # 提取文件名用于表单提交
    upload_filename = os.path.basename(i[1]).encode('utf-8')
    info_list.append(curl.FORM_BUFFER)
    info_list.append(upload_filename)
    info_list.append(curl.FORM_BUFFERPTR)
    info_list.append(file_content)
    info_list.append(curl.FORM_BUFFERLENGTH)
    info_list.append(len(file_content))

如果不想手动读取文件内容，也可以将文件路径的编码从UTF-8改为Windows系统本地ANSI编码（可通过sys.getfilesystemencoding()获取），但该方案存在兼容缺陷，若路径包含超出当前系统ANSI编码范围的字符仍会失败，不推荐使用。

内容的提问来源于stack exchange，提问作者Felix Rösch