Build a JSON-to-PDF invoice converter

Here’s a complete implementation of a JSON-to-PDF invoice converter using Python. It reads invoice data from a JSON file or object and generates a styled PDF using the reportlab library.

🔧 Requirements

Install reportlab before running:

bash
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pip install reportlab

🧾 Python Code: JSON to PDF Invoice Converter

python
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import json
from reportlab.lib.pagesizes import A4
from reportlab.lib import colors
from reportlab.pdfgen import canvas
from reportlab.platypus import Table, TableStyle, Paragraph, SimpleDocTemplate
from reportlab.lib.styles import getSampleStyleSheet

def generate_invoice(json_data, output_filename="invoice.pdf"):
    data = json.loads(json_data) if isinstance(json_data, str) else json_data
    doc = SimpleDocTemplate(output_filename, pagesize=A4)
    elements = []
    styles = getSampleStyleSheet()
    styleN = styles["Normal"]
    styleH = styles["Heading1"]

    # Invoice Header
    elements.append(Paragraph(f"Invoice #{data['invoice_no']}", styleH))
    elements.append(Paragraph(f"Date: {data['date']}", styleN))
    elements.append(Paragraph(f"Due Date: {data['due_date']}", styleN))
    elements.append(Paragraph(f"Bill To: {data['customer']['name']}", styleN))
    elements.append(Paragraph(f"{data['customer']['address']}", styleN))
    elements.append(Paragraph(f"Email: {data['customer']['email']}", styleN))
    elements.append(Paragraph("<br/>", styleN))  # spacing

    # Table of items
    table_data = [["Item", "Description", "Qty", "Unit Price", "Total"]]
    for item in data["items"]:
        total_price = item["quantity"] * item["unit_price"]
        table_data.append([
            item["name"],
            item.get("description", ""),
            str(item["quantity"]),
            f"${item['unit_price']:.2f}",
            f"${total_price:.2f}"
        ])

    # Table Style
    table = Table(table_data, colWidths=[80, 180, 50, 80, 80])
    table.setStyle(TableStyle([
        ("BACKGROUND", (0, 0), (-1, 0), colors.grey),
        ("TEXTCOLOR", (0, 0), (-1, 0), colors.whitesmoke),
        ("ALIGN", (2, 1), (-1, -1), "CENTER"),
        ("GRID", (0, 0), (-1, -1), 0.5, colors.black),
        ("FONTNAME", (0, 0), (-1, 0), "Helvetica-Bold"),
        ("BOTTOMPADDING", (0, 0), (-1, 0), 10),
    ]))

    elements.append(table)

    # Total Section
    elements.append(Paragraph("<br/>", styleN))
    elements.append(Paragraph(f"Subtotal: ${data['subtotal']:.2f}", styleN))
    elements.append(Paragraph(f"Tax ({data['tax_percent']}%): ${data['tax']:.2f}", styleN))
    elements.append(Paragraph(f"Total: <b>${data['total']:.2f}</b>", styleN))

    # Footer
    elements.append(Paragraph("<br/><br/>Thank you for your business!", styleN))

    doc.build(elements)
    print(f"Invoice saved as {output_filename}")

# Sample JSON
sample_invoice = {
    "invoice_no": "INV-1001",
    "date": "2025-05-17",
    "due_date": "2025-06-01",
    "customer": {
        "name": "John Doe",
        "address": "123 Elm Street, Springfield, IL 62704",
        "email": "john.doe@example.com"
    },
    "items": [
        {"name": "Web Design", "description": "Homepage redesign", "quantity": 1, "unit_price": 500.00},
        {"name": "Hosting", "description": "Annual hosting plan", "quantity": 1, "unit_price": 120.00},
        {"name": "Maintenance", "description": "Monthly support", "quantity": 6, "unit_price": 50.00}
    ],
    "subtotal": 920.00,
    "tax_percent": 10,
    "tax": 92.00,
    "total": 1012.00
}

# Generate the PDF
generate_invoice(sample_invoice)

✅ Features

• Supports multiline descriptions and dynamic item list

• Customizable tax, subtotal, and totals

• Basic styling with a header and table format

Let me know if you want:

• HTML-to-PDF version

• Flask web interface

• Command-line version

• Multi-language currency formatting