Question

当我尝试运行此功能时，它会给我这个错误“ UnboundLocalError：赋值之前引用的局部变量'labels'”可以帮助我

@app.route('/', methods=['GET', 'POST'])
def upload_file():
    if request.method == 'POST' and 'photo' in request.files:
        filename = photos.save(request.files['photo'])
        file_url = photos.url(filename)
        with io.open(filename, 'rb') as image_file:
            content = image_file.read()
        image = types.Image(content=content)
        response = vision_client.label_detection(image=image)
        labels = response.label_annotations()

    return render_template('index.html', thelabels=labels)

Answer 1

仅当labels语句返回if时才实例化函数中的True变量，否则将永远不会创建该变量。

如果初始检查未返回else（或在True之前为labels提供默认值，则需要设置if语句来创建变量声明，如艾哈迈德的建议）：

@app.route('/', methods=['GET', 'POST'])
def upload_file():
    # Option 1: give `labels` a default value here - Doesn't have to be `None`
    labels = None
    if request.method == 'POST' and 'photo' in request.files:
        filename = photos.save(request.files['photo'])
        file_url = photos.url(filename)
        with io.open(filename, 'rb') as image_file:
            content = image_file.read()
        image = types.Image(content=content)
        response = vision_client.label_detection(image=image)
        labels = response.label_annotations()

    else: # Option 2: set `labels` to `None` in an `else` statement in case the `if` statement check returns False
        labels = None

    return render_template('index.html', thelabels=labels)

Answer 2

由于在labels语句中定义了变量if，导致了本地错误。在函数中定义

@app.route('/', methods=['GET', 'POST'])
def upload_file():
    labels = ''
    if request.method == 'POST' and 'photo' in request.files:
        filename = photos.save(request.files['photo'])
        file_url = photos.url(filename)
        with io.open(filename, 'rb') as image_file:
            content = image_file.read()
        image = types.Image(content=content)
        response = vision_client.label_detection(image=image)
        labels = response.label_annotations()
    return render_template('index.html', thelabels=labels)

渲染模板时，请检查模板中thelabels是否为''

希望有帮助

UnboundLocalError：分配前已引用局部变量“标签”

2 个答案: