与“无法解码JSON对象"相比，显示更好的错误消息. [英] Displaying better error message than "No JSON object could be decoded"

问题描述

Python代码从一些复杂的JSON长文件中加载数据:

Python code to load data from some long complicated JSON file:

with open(filename, "r") as f:
  data = json.loads(f.read())

(注意:最佳代码版本应为:

(note: the best code version should be:

with open(filename, "r") as f:
  data = json.load(f)

但都表现出相似的行为)

but both exhibit similar behavior)

对于许多类型的JSON错误(缺少分隔符，字符串中的反斜杠不正确等)，这会打印出一条非常有用的消息，其中包含找到JSON错误的行号和列号.

For many types of JSON error (missing delimiters, incorrect backslashes in strings, etc), this prints a nice helpful message containing the line and column number where the JSON error was found.

但是，对于其他类型的JSON错误(包括经典的在列表中的最后一项上使用逗号"，以及诸如大写的true/false等其他内容)，Python的输出仅为:

However, for other types of JSON error (including the classic "using comma on the last item in a list", but also other things like capitalising true/false), Python's output is just:

Traceback (most recent call last):
  File "myfile.py", line 8, in myfunction
    config = json.loads(f.read())
  File "c:\python27\lib\json\__init__.py", line 326, in loads
    return _default_decoder.decode(s)
  File "c:\python27\lib\json\decoder.py", line 360, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "c:\python27\lib\json\decoder.py", line 378, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

对于这种类型的ValueError，如何让Python告诉您JSON文件中的错误在哪里?

For that type of ValueError, how do you get Python to tell you where is the error in the JSON file?

推荐答案

我发现，在内置json模块含糊不清的许多情况下，simplejson模块给出了更多的描述性错误.例如，对于列表中最后一个项目后面有逗号的情况:

I've found that the simplejson module gives more descriptive errors in many cases where the built-in json module is vague. For instance, for the case of having a comma after the last item in a list:

json.loads('[1,2,]')
....
ValueError: No JSON object could be decoded

这不是很描述. simplejson的相同操作:

which is not very descriptive. The same operation with simplejson:

simplejson.loads('[1,2,]')
...
simplejson.decoder.JSONDecodeError: Expecting object: line 1 column 5 (char 5)

好多了！同样，对于其他常见错误，例如将True大写.

Much better! Likewise for other common errors like capitalizing True.

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