JSON to CSV Converter
This utility converts a JSON file (specifically a list of objects) into a CSV file. It automatically detects all unique keys across the JSON objects to create the CSV headers, ensuring no data is lost even if some objects have missing fields.
Modules Used:
- json: To parse the input JSON file.
- csv: To write the output CSV file.
- argparse: To handle command-line arguments.
The Code
Save this as json2csv.py.
import json
import csv
import argparse
import sys
def convert_json_to_csv(json_file, csv_file):
try:
# 1. Load JSON Data
with open(json_file, 'r', encoding='utf-8') as jf:
data = json.load(jf)
# Validate structure: Expecting a list of dictionaries
if not isinstance(data, list):
print("Error: JSON root must be a list of objects (e.g., [{}, {}]).")
return
if not data:
print("Error: JSON file is empty.")
return
# 2. Determine Headers
# Collect all unique keys from all objects to handle inconsistent schemas
headers = set()
for entry in data:
if isinstance(entry, dict):
headers.update(entry.keys())
# Sort headers for consistent output
fieldnames = sorted(list(headers))
# 3. Write CSV
with open(csv_file, 'w', newline='', encoding='utf-8') as cf:
writer = csv.DictWriter(cf, fieldnames=fieldnames)
writer.writeheader()
# writerows automatically handles missing keys by leaving cells empty
writer.writerows(data)
print(f"Successfully converted '{json_file}' to '{csv_file}'")
print(f"Processed {len(data)} records.")
except FileNotFoundError:
print(f"Error: File '{json_file}' not found.")
except json.JSONDecodeError:
print(f"Error: Failed to decode JSON from '{json_file}'. Check syntax.")
except Exception as e:
print(f"An error occurred: {e}")
if __name__ == "__main__":
parser = argparse.ArgumentParser(description="JSON to CSV Converter")
parser.add_argument("input", help="Input JSON file path")
parser.add_argument("output", help="Output CSV file path")
args = parser.parse_args()
convert_json_to_csv(args.input, args.output)Usage
python json2csv.py data.json output.csv