如何从python中的html获取下拉输入的值？

Question

我正在创建一个应用程序，该应用程序从图像中获取文本并将其转换为用户从下拉菜单中选择的语言。此下拉菜单基于一个词典，该词典具有所有google翻译支持的语言及其相应的代码。但是，我在从此下拉菜单中获取输入并将其放回python代码进行翻译时遇到了麻烦。翻译的代码可以正常工作，因为我可以输入固定的语言，它将翻译成该语言。但是如何根据用户输入来确定目标语言。我尝试将语言下拉列表以您选择图像的相同形式，使用request.method = "POST"，然后使用target = request.args['lang_target']，将其命名为“ lang_target”。但这返回错误：werkzeug.exceptions.HTTPException.wrap.<locals>.newcls: 400 Bad Request: KeyError: 'lang_target'

Python：

def Lang_target():
    language_targ={
        'af': 'Afrikaans',              'sq':'Albanian',    'ar': 'Arabic',     'az': 'Azerbaijani',
        'be': 'Belarusian',             'bn': 'Bengali',    'ca': 'Catalan',    'zh-CN': 'Chinese Simplified',
        'zh-TW': 'Chinese Traditional', 'hr': 'Croatian',   'cs': 'Czech',      'da': 'Danish',     
        'nl': 'Dutch',                  'en': 'English',    'eo': 'Esperanto',  'et': 'Estonian',
        'tl': 'Filipino',               'fi': 'Finnish',    'fr': 'French',     'gl': 'Galician',   
        'ka': 'Georgian',               'de': 'German',     'el': 'Greek',      'gu': 'Gujarati',
        'ht': 'Haitian Creole',         'iw': 'Hebrew',     'hi': 'Hindi',      'hu': 'Hungarian',
        'is': 'Icelandic',              'ga': 'Irish',      'it': 'Italian',    'id': 'Indonesian',
        'ja': 'Japanese',               'kn': 'Kannada',    'ko': 'Korean',     'la': 'Latin',
        'lv': 'Latvian',                'lt': 'Lithuanian', 'mk': 'Macedonian', 'ms': 'Malay',
        'mt': 'Maltese',                'no': 'Norwegian',  'fa': 'Persian',    'pl': 'Polish', 
        'pt': 'Portuguese',             'ro': 'Romanian',   'ru': 'Russian',    'sr': 'Serbian',
        'sk': 'Slovak',                 'es': 'Spanish',    'sl': 'Slovenian',  'sw': 'Swahili',
        'sv': 'Swedish',                'ta': 'Tamil',      'te': 'Telugu',     'th': 'Thai',
        'tr': 'Turkish',                'uk': 'Ukrainian',  'ur': 'Urdu',       'vi': 'Vietnamese',             
        'cy': 'Welsh',                  'yi': 'Yiddish',
    }
    return language_targ

@app.route('/selectImage')
def selectImage():
    fn = image_name()
    language_target = Lang_target()
    return render_template("selectImage.html", image_name=image_name, fn=fn, language_target=language_target)

@app.route('/getfileHelper', methods=['GET','POST'])
def getfileHelper():
    if request.method == 'POST':
        #get the file name
        #hfile upload: ttps://www.tutorialspoint.com/flask/flask_file_uploading.htm
        file = request.files['imgfile']
        filename = secure_filename(file.filename)   #from werkzeug import secure_filename
        #TEMP PRINT STATEMENT
        #print("filename    : ",filename)
        #if the user did not select a file return to the selectImage.html page
        if file.filename == '':
            flash("No file selected. Please select an image file")
            return render_template('selectImage.html')
        #call the funcion whihc does the AI
        texts = detect_text('static/images/'+filename)

        text_translations = [] #emty list for dictionary of original text and translation
        #loop through list of texts, call the transpate AI function,
        #  add origi nal text and tranlation to list of dictionaries
        for text in texts:
            #print('\n"{}"'.format(text.description))
            translate_client = translate.Client()  # Instantiates a client
            translate_text = text.description  # The text to translate
            source = 'en'  # The source language
            target = request.args['lang_target']  # The target language 
            # Translate text into targget language
            translation = translate_client.translate(translate_text, source_language=source, target_language=target)
            # add original text and translation as a dictionary to a list
            text_translations.append({'text':translate_text, 'translation':translation['translatedText']})

            db_append(filename, translate_text, translation['translatedText'])
        #print('TRANSLATIONS')
        #print(text_translations)
    return render_template('home.html', filename=filename, text_translations=text_translations)

HTML

<div class="container" style="padding-bottom: 100%; background-color: #f4976c; color: #66fcf1; ">
        <h1>Select image...</h1>
        <div style="height:100px;"></div>

        <form action="getfileHelper" method="POST" enctype="multipart/form-data">
            Project file path: <input type="file" name="imgfile">
            <br>
            <select name="lang_target">
                {% for x in language_target%} 
                    <option value='1'> {{ language_target[x] }}</option>
                {% endfor %}
            </select>
            <br>
            <input type="submit" value="Submit">
        </form>
        <br>

        {% if filename %}
            <img src="{{ url_for('static', filename='images/'+filename) }} " style="max-width:300px">
        {% endif %}

Answer 1

request.args查看URL参数，但是您正在通过POST发送回数据。尝试将request.args替换为request.form

Answer 2

像flask html对一样替换key, value中的for循环。用以下几行替换您的代码（我假设您的flask重定向和参数正确传递了）。

<select name="lang_target">
  {% for key,value in language_target%}
    <option value='{{ key }}'> {{ value }}</option>
  {% endfor %}
</select>