Python 局部变量'；s'；分配前参考

我应该如何修复此引用错误？你能帮我解释一下为什么会这样吗

def detectobjects(image2):
    print("===== Detect Objects - local =====")
    image = open(image, "rb")
    # Call API with local image
    detect_objects_results_local = computervision_client.detect_objects_in_stream(image)
    print("Detecting objects in local image:")
    if len(detect_objects_results_local.objects) == 0:
        print("No objects detected.")
    else:
        s=""
        for object in detect_objects_results_local.objects:
            #print("Object : {} with confidence: {}".format(\object.object_property,object.confidence))            
            obj="object= {} , confidence= {} ".format(object.object_property, object.confidence)
            s+=obj
    return s

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您需要在if-else语句之外定义

s

def detectobjects(image2):
print("===== Detect Objects - local =====")
image = open(image, "rb")
# Call API with local image
detect_objects_results_local = computervision_client.detect_objects_in_stream(image)
print("Detecting objects in local image:")
s=""
if len(detect_objects_results_local.objects) == 0:
    print("No objects detected.")
else:
    for object in detect_objects_results_local.objects:
        #print("Object : {} with confidence: {}".format(\object.object_property,object.confidence))            
        obj="object= {} , confidence= {} ".format(object.object_property, object.confidence)
        s+=obj
return s

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有什么不清楚的错误？如果未检测到任何对象，则无法

返回s

。。。也许你应该修正缩进？这是假设一个空字符串是一个有效的返回条件，而不是none。考虑到正在构建的字符串，空字符串可能是好的，尽管对象/置信字符串的列表（可能是空的）可能会更干净，如果不是元组列表的话。如果需要，让调用者构造一个对象/置信对字符串。