无法使用ijson访问顶级元素? [英] No access to top level elements with ijson?

问题描述

我一直在尝试使用Python的ijson库解析JSON文件.当查看二级元素或使用解析器时，此方法有效，但我更希望直接查看顶级元素的方便.

I've been trying to parse a JSON file with Python's ijson library. This works when looking at second-level elements or when using a parser, but I'd prefer the convenience of looking at top level elements directly.

JSON的基本格式如下:

The JSON is basically formatted like this:

{"foo":{"a":1,"b":2},"bar":{"c":3,"d":4}}

所以，没什么好看的.我想做的是以一种迭代方式遍历它，从而产生"foo"及其值/"bar"及其每次迭代的值. (所以，就像我要json.loads这件事一样.)我的代码如下-我知道它不会同时产生两者，我只是在测试:

So, nothing fancy. What I'd like to do is iterate through it in a way that yields "foo" and its value / "bar" and its value per iteration. (So just like if I were to json.loads this thing.) My code is the following - I know it's not going to yield both, I was just testing:

f=open('test')
i=ijson.items(f,'item')
for j in i:
    print j

items()函数的语法是我从获得的语法stackoverflow .

但是，奇怪的是，循环确实需要时间，但是实际上并没有输出任何东西. (即使我在其中放置print 'qyx'也不是这样，所以我不知道它在做什么.)如果我修改items()函数以解析foo.item，它确实可以工作，但是我能找到的很少的信息表明它也应该适用于顶层.另外，如果我使用以下命令，它可以工作，但是更加不透明:

However, strangely, the loop does take time, but it doesn't actually output anything. (Not even if I put a print 'qyx' in there, so I don't know what it's doing.) If I modify the items() function to parse foo.item, it does work, but what little info I can find indicates that it should work for the top level as well. Plus if I use the following, it works, but it's much more opaque:

i=ijson.parse(f)
for prefix, event, value in i:
   if not prefix or event == 'map_key' or ( '.' in prefix and event in ('start_map','end_map') ):
       continue
   print prefix, event, value

这将输出

foo start_map None
foo.a number 1
foo.b number 2
foo end_map None
bar start_map None
bar.c number 3
bar.d number 4
bar end_map None

...可以进行处理以生成"foo"和{"a":1,"b":2}等，但这要麻烦得多.

... which could be processed to yield "foo" and {"a":1,"b":2} etc, but it's much more of a hassle.

推荐答案

尝试一下:

f = open('test')
json_obj = ijson.items(f,'').next() # '' loads everything as only one object.
for (key, value) in json_obj.items():
    print key + " -> " + str(value)

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