[FIXED] How to get error location from json.loads in Python

Issue

When I use json.loads in Python 3 and catch any resulting errors, like:

try:
  data = json.loads(string)
except ValueError as err:
  print(err)

I get a helpful message like:

Expecting ',' delimiter: line 12 column 12 (char 271)

I would like to be able to display this to the user, along with exactly the location which is causing the problem (I am reading in user-written JSON). How can I get out the line and column?

I could use a regex on err, but that feels like a bad idea, as I don't know if this message is internationalised, and could change in different versions of python. Is there a better way?

Solution

In Python 3.5 and up, a specialized JSONDecodeError will be raised instead of ValueError. It has several useful attributes - quoting from the documentation:

msg: The unformatted error message.
doc: The JSON document being parsed.
pos: The start index of doc where parsing failed.
lineno: The line corresponding to pos.
colno: The column corresponding to pos.

Answered By - Karl Knechtel

Answer Checked By - David Goodson (PHPFixing Volunteer)