麻烦与蟒蛇

Question

阅读JSON文件，我有一个JSON文件看起来像这样：

[ 
{ 
    "image_path": "train640x480/2d4_2.bmp", 
    "rects": [ 
    { 
    "y2": 152.9, 
    "y1": 21.2, 
    "x2": 567.3, 
    "x1": 410.8 
    } 
    ] 
}, 
{ 
    "image_path": "train640x480/1dd_1.bmp", 
    "rects": [ 
    { 
    "y2": 175.1, 
    "y1": 74.7, 
    "x2": 483.8, 
    "x1": 230.8 
    } 
    ] 
} 
] 

当我做

H = {} 
with open('train.json', 'r') as json_data: 
     H = json.load(json_data) 
    print(H) 

它打印出

如何访问每个图像的矩形值？我试过

H['image_path:'][os.path.join(directory, filename)] 

但返回

TypeError: list indices must be integers or slices, not str 

任何帮助，将不胜感激。

Answer 1

您的json文件包含列表词典，这意味着您首先需要在访问词典的内容之前遍历列表。

例如

for items in H: 
    if items['image_path'] == os.path.join(directory, filename): 
     print items['rects'] 

如果你的json看起来像这样，你将能够像你期待的那样访问条目。

{ 
    "train640x480/2d4_2.bmp": 
     { 
      "rects": [ 
       { 
        "y2": 152.9, 
        "y1": 21.2, 
        "x2": 567.3, 
        "x1": 410.8 

       } 
      ] 
     }, 

    "train640x480/1dd_1.bmp": 
     { 
      "rects": [ 
       { 
        "y2": 175.1, 
        "y1": 74.7, 
        "x2": 483.8, 
        "x1": 230.8 
       } 
      ] 
     } 
} 

例如，

print H['train640x480/2d4_2.bmp']['rects] 

Answer 2

您应该首先将一个数字作为索引访问第一个列表。你的json数据的结构是一个列表，然后是字典列表，然后列出顶点字典。您的查询应该是

H[0]["rects"][0] # the fist rectangle dictionary 

而且

H[1]["rects"][0] # the second rectangle dictionary 

Answer 3

试试这个代码

print H[0]["image_path"] 
print H[0]["rects"][0]["y2"] 


print H[1]["image_path"] 
print H[1]["rects"][0]["y2"]