Common JSON Reading Errors in Python - Fixes & Solutions

# ❌ ERROR
with open('config.json', 'r') as f:
    data = json.load(f)
# FileNotFoundError: [Errno 2] No such file or directory

# ✅ FIX

import os
from pathlib import Path

file_path = Path('config.json')
if file_path.exists():
    with open(file_path, 'r') as f:
        data = json.load(f)
else:
    print(f"File not found: {file_path.absolute()}")

# ❌ Common causes:
# 1. Trailing comma
{"name": "Alice",}

# 2. Single quotes
{'name': 'Bob'}

# 3. Missing quotes
{name: "Charlie"}

# ✅ Universal fix with line numbers

import json

def safe_json_load(filepath: str) -> dict:
    try:
        with open(filepath, 'r', encoding='utf-8') as f:
            return json.load(f)
    except json.JSONDecodeError as e:
        print(f"JSON Error at line {e.lineno}, col {e.colno}: {e.msg}")
        print(f"Near: ...{e.doc[max(0,e.pos-20):e.pos+20]}...")
        return {}

# ❌ ERROR
json_str = '{"name": "Alice"} extra text'
json.loads(json_str)
# JSONDecodeError: Extra data: line 1 column 18

# ✅ FIX - Parse only valid JSON portion

import json

def parse_partial_json(text: str):
    try:
        parsed, end = json.JSONDecoder().raw_decode(text)
        return parsed, text[:end].strip()
    except json.JSONDecodeError:
        return {}, text

# ❌ ERROR
with open('data.json', 'r') as f:
    json.load(f)
# UnicodeDecodeError: 'charmap' codec can't decode

# ✅ ALWAYS specify encoding
with open('data.json', 'r', encoding='utf-8-sig') as f:
    data = json.load(f)

# Auto-detect encoding

import chardet

with open('data.json', 'rb') as f:
    raw = f.read()
    encoding = chardet.detect(raw)['encoding']
    data = json.loads(raw.decode(encoding))

import os
import stat

def can_read_file(filepath: str) -> bool:
    if os.path.exists(filepath):
        st = os.stat(filepath)
        return (st.st_mode & stat.S_IRUSR) != 0
    return False

if can_read_file('config.json'):
    with open('config.json', 'r') as f:
        data = json.load(f)

# ❌ Wrong - treating JSONL as single JSON
with open('data.jsonl') as f:
    data = json.load(f)  # Fails at line 2!

# ✅ Correct JSONL parsing
jsonl_data = []
with open('data.jsonl', 'r') as f:
    for line in f:
        if line.strip():
            jsonl_data.append(json.loads(line))

{
  "name": "Alice",
  "age": 25,  // ❌ Trailing comma + comment
}

import re

def clean_json(text: str) -> str:
    # Remove C-style comments
    text = re.sub(r'//.*', '', text)
    text = re.sub(r'/\*.*?\*/', '', text, flags=re.DOTALL)
    # Remove trailing commas
    text = re.sub(r',\s*([}\]])', r'\1', text)
    return text

json_str = clean_json(raw_json)
data = json.loads(json_str)

{
  "version": "0.2.0",
  "configurations": [
    {
      "name": "Debug JSON Errors",
      "type": "python",
      "request": "launch",
      "program": "${file}",
      "console": "integratedTerminal",
      "exceptionBreakpointFilters": {
        "raised": {
          "filters": ["pythonException"]
        }
      }
    }
  ]
}

import json
from pathlib import Path
from typing import Any, Dict

class SafeJSONReader:
    @staticmethod
    def read(file_path: str | Path, *, default: Dict[str, Any] = None) -> Dict[str, Any]:
        if default is None:
            default = {}
        
        path = Path(file_path)
        if not path.exists():
            print(f"⚠️  File not found: {path.absolute()}")
            return default
        
        try:
            with open(path, 'r', encoding='utf-8-sig') as f:
                return json.load(f)
        except json.JSONDecodeError as e:
            print(f"❌ JSON Error: line {e.lineno}:{e.colno} - {e.msg}")
            return default
        except UnicodeDecodeError:
            print("❌ Encoding error - try saving as UTF-8")
            return default
        except Exception as e:
            print(f"❌ Unexpected: {e}")
            return default

# Usage
data = SafeJSONReader.read('config.json')

python -m json.tool config.json
# Pretty prints valid JSON, errors on invalid