find lines longer than X in JSON and delete the whole object

Question

I have a huge JSON Array with multiple thousand objects and I need to filter all objects where the text field is too long (say 200 chars).

I've found a lot of SED/AWK advices to find a line with a certain length, but how can I delete that line AND the 1 before and the 2 after it; so that the whole JSON object is deleted?

The structure is like follows:

{ "text": "blah blah blah", "author": "John Doe" }

Thanks!

Answer 1

Here's a Python script that does what you want:

#!/usr/bin/env python
# -*- coding: ascii -*-
"""filter.py"""

import sys

# Get the file and the maximum line-length as command-line arguments
filepath = sys.argv[1]
maxlen = int(sys.argv[2])

# Initialize a list to store the unfiltered lines
lines = []

# Read the data file line-by-line
jsonfile = open(filepath, 'r')
for line in jsonfile:

    # Only consider non-empty lines
    if line:

        # For "text" lines that are too line, remove the previous line
        # and also skip the next two line
        if "text" in line and len(line) > maxlen: 
            lines.pop()
            next(jsonfile)
            next(jsonfile)
        # Add all other lines to the list
        else:
            lines.append(line)

# Strip trailing comma from the last object
lines[-2] = lines[-2].replace(',', '')

# Output the lines from the list
for line in lines:
    sys.stdout.write(line)

You could run it like this:

python filter.py data.json 34

Suppose you had the following data file:

[
    {
    "text": "blah blah blah one",
    "author": "John Doe"
    },
    {
    "text": "blah blah blah two",
    "author": "John Doe"
    },
    {
    "text": "blah blah blah three",
    "author": "John Doe"
    }
]

Then running the script as described would produce the following output:

[
    {
    "text": "blah blah blah one",
    "author": "John Doe"
    },
    {
    "text": "blah blah blah two",
    "author": "John Doe"
    }
]