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Error Handling

PDFDancer provides detailed exception handling to help you identify and resolve issues quickly. All exceptions include descriptive error messages and context.

Exception Hierarchy​

All exceptions inherit from PdfDancerException:

  • PdfDancerException - Base exception for all PDFDancer errors
    • ValidationException - Client-side validation errors (missing token, invalid coordinates, etc.)
    • FontNotFoundException - Font not found on the service
    • HttpClientException - HTTP transport or server errors
    • SessionException - Session creation or management failures
from pdfdancer.exceptions import (
    PdfDancerException,
    ValidationException,
    FontNotFoundException,
    HttpClientException,
    SessionException
)

Handling Validation Errors​

from pdfdancer import PDFDancer
from pdfdancer.exceptions import ValidationException

try:
    # Missing required token
    with PDFDancer.open("document.pdf") as pdf:
        pass
except ValidationException as e:
    print(f"Validation error: {e}")
    # Output: "Validation error: API token is required"

try:
    # Invalid coordinates
    with PDFDancer.open("document.pdf", token="valid-token") as pdf:
        pdf.new_paragraph() \
            .text("Test") \
            .font("Helvetica", 12) \
            .at(page_number=-1, x=100, y=500) \
            .add()
except ValidationException as e:
    print(f"Validation error: {e}")
    # Output: "Validation error: Page number must be positive"

Handling Font Errors​

from pdfdancer import PDFDancer
from pdfdancer.exceptions import FontNotFoundException

try:
    with PDFDancer.open("document.pdf") as pdf:
        pdf.new_paragraph() \
            .text("Hello") \
            .font("NonExistentFont", 12) \
            .at(page_number=1, x=100, y=500) \
            .add()
except FontNotFoundException as e:
    print(f"Font not found: {e}")
    # Fallback to default font
    with PDFDancer.open("document.pdf") as pdf:
        pdf.new_paragraph() \
            .text("Hello") \
            .font("Helvetica", 12) \
            .at(page_number=1, x=100, y=500) \
            .add()
        pdf.save("output.pdf")

Handling HTTP and Session Errors​

from pdfdancer import PDFDancer
from pdfdancer.exceptions import (
    HttpClientException,
    SessionException,
    PdfDancerException
)

try:
    with PDFDancer.open(
        "document.pdf",
        token="invalid-token",
        base_url="https://api.pdfdancer.com"
    ) as pdf:
        pdf.save("output.pdf")

except SessionException as e:
    print(f"Session error: {e}")
    # Session creation failed, possibly due to invalid token

except HttpClientException as e:
    print(f"HTTP error: {e}")
    # Network or server error

except PdfDancerException as e:
    print(f"Unexpected error: {e}")
    # Catch-all for other PDFDancer errors

Complete Error Handling Pattern​

from pdfdancer import PDFDancer, Color
from pdfdancer.exceptions import (
    ValidationException,
    FontNotFoundException,
    HttpClientException,
    SessionException,
    PdfDancerException
)

def process_pdf(input_path: str, output_path: str) -> bool:
    """
    Process a PDF with comprehensive error handling.

    Returns True on success, False on failure.
    """
    try:
        with PDFDancer.open(input_path) as pdf:
            # Find and edit paragraphs
            paragraphs = pdf.page(1).select_paragraphs_starting_with("Invoice")

            if paragraphs:
                paragraphs[0].edit() \
                    .replace("PAID") \
                    .color(Color(0, 128, 0)) \
                    .apply()

            # Add watermark
            pdf.new_paragraph() \
                .text("CONFIDENTIAL") \
                .font("Helvetica-Bold", 48) \
                .color(Color(200, 200, 200)) \
                .at(page_number=1, x=150, y=400) \
                .add()

            pdf.save(output_path)
            return True

    except ValidationException as e:
        print(f"Validation failed: {e}")
        print("Check your input parameters and try again.")
        return False

    except FontNotFoundException as e:
        print(f"Font error: {e}")
        print("Using fallback font...")
        # Retry with fallback font
        try:
            with PDFDancer.open(input_path) as pdf:
                pdf.new_paragraph() \
                    .text("CONFIDENTIAL") \
                    .font("Helvetica", 48) \
                    .color(Color(200, 200, 200)) \
                    .at(page_number=1, x=150, y=400) \
                    .add()
                pdf.save(output_path)
                return True
        except Exception as retry_error:
            print(f"Retry failed: {retry_error}")
            return False

    except SessionException as e:
        print(f"Session error: {e}")
        print("Check your API token and network connection.")
        return False

    except HttpClientException as e:
        print(f"HTTP error: {e}")
        print("The API server may be unavailable. Try again later.")
        return False

    except PdfDancerException as e:
        print(f"PDFDancer error: {e}")
        return False

    except Exception as e:
        print(f"Unexpected error: {e}")
        return False


# Usage
success = process_pdf("invoice.pdf", "processed_invoice.pdf")
if success:
    print("PDF processed successfully!")
else:
    print("PDF processing failed.")

Common Error Scenarios​

Missing API Token​

# Error: ValidationException - API token is required
# Solution: Set PDFDANCER_TOKEN environment variable or pass token explicitly

import os
os.environ['PDFDANCER_TOKEN'] = 'your-token'

# Or pass explicitly
with PDFDancer.open("doc.pdf", token="your-token") as pdf:
    pass

File Not Found​

from pathlib import Path

pdf_path = Path("document.pdf")

if not pdf_path.exists():
    print(f"Error: File {pdf_path} not found")
else:
    with PDFDancer.open(pdf_path) as pdf:
        pdf.save("output.pdf")

Network Timeout​

# Increase timeout for large PDFs or slow connections
with PDFDancer.open(
    "large-document.pdf",
    timeout=120  # 120 seconds
) as pdf:
    pdf.save("output.pdf")

Next Steps​

  • Advanced – Learn advanced patterns and optimization techniques
  • Examples – See complete working examples with error handling