Form Fields and Interactive Elements

def update_page_form_field_values(
    self,
    page: PageObject | list[PageObject] | None,
    fields: dict[str, str | list[str] | tuple[str, str, float]],
    flags: int = 0,
    auto_regenerate: bool = True,
    flatten: bool = False
) -> None:
    """
    Update form field values for given page(s) from a fields dictionary.
    
    Args:
        page: Page(s) to update, or None for all pages
        fields: Dictionary mapping field names to values
            - str: Simple text value
            - list[str]: Multiple values for choice fields
            - tuple[str, str, float]: (value, export_value, font_size)
        flags: Form field flags for appearance
        auto_regenerate: Whether to regenerate field appearances automatically
        flatten: Whether to flatten fields after updating (make non-editable)
    """

def set_need_appearances_writer(self, state: bool = True) -> None:
    """
    Set the NeedAppearances flag for form fields.
    
    The NeedAppearances flag indicates whether the PDF viewer should
    automatically generate appearances for form fields or use embedded
    appearances.
    
    Args:
        state: Whether to enable automatic appearance generation
    """

def reattach_fields(self, page: PageObject | None = None) -> list[DictionaryObject]:
    """
    Parse page annotations to find orphan fields and reattach them
    to the document's form field structure.
    
    Args:
        page: Page to analyze, or None to analyze all pages
        
    Returns:
        List of reattached field dictionary objects
    """

from pypdf import PdfReader, PdfWriter

# Read PDF with form fields
reader = PdfReader("form.pdf")
writer = PdfWriter()

# Copy pages to writer
for page in reader.pages:
    writer.add_page(page)

# Update form field values
field_updates = {
    "FirstName": "John",
    "LastName": "Doe", 
    "Email": "john.doe@example.com",
    "Age": "30",
    "Subscription": "Premium"  # Checkbox or choice field
}

# Update all pages with form fields
writer.update_page_form_field_values(None, field_updates)

# Save updated PDF
with open("filled_form.pdf", "wb") as output:
    writer.write(output)

from pypdf import PdfReader, PdfWriter

reader = PdfReader("complex_form.pdf")
writer = PdfWriter()
writer.append_pages_from_reader(reader)

# Complex field values with formatting
advanced_fields = {
    # Simple text field
    "name": "Alice Smith",
    
    # Choice field with multiple selections
    "interests": ["Technology", "Science", "Art"],
    
    # Field with custom font size and export value
    "salary": ("75000", "75k", 10.0),  # (display_value, export_value, font_size)
    
    # Boolean/checkbox field
    "agree_terms": "Yes"
}

# Update with custom flags and flattening
writer.update_page_form_field_values(
    page=None,  # All pages
    fields=advanced_fields,
    flags=0,
    auto_regenerate=True,  # Generate field appearances
    flatten=True  # Make fields non-editable
)

with open("processed_form.pdf", "wb") as output:
    writer.write(output)

from pypdf import PdfReader, PdfWriter

reader = PdfReader("damaged_form.pdf")
writer = PdfWriter()
writer.append_pages_from_reader(reader)

# Repair orphaned form fields
for page in writer.pages:
    orphaned_fields = writer.reattach_fields(page)
    if orphaned_fields:
        print(f"Reattached {len(orphaned_fields)} orphaned fields")

# Ensure appearances are properly generated
writer.set_need_appearances_writer(True)

with open("repaired_form.pdf", "wb") as output:
    writer.write(output)

from pypdf import PdfReader, PdfWriter
import json

def process_form_batch(template_path: str, data_file: str, output_dir: str):
    """Process multiple form submissions from JSON data."""
    
    # Load form data
    with open(data_file, 'r') as f:
        submissions = json.load(f)
    
    template_reader = PdfReader(template_path)
    
    for i, submission in enumerate(submissions):
        # Create new writer for each submission
        writer = PdfWriter()
        writer.append_pages_from_reader(template_reader)
        
        # Update form fields
        writer.update_page_form_field_values(
            page=None,
            fields=submission,
            auto_regenerate=True
        )
        
        # Save individual form
        output_path = f"{output_dir}/form_{i+1:03d}.pdf"
        with open(output_path, "wb") as output:
            writer.write(output)
        
        print(f"Generated form {i+1}: {output_path}")

# Use batch processor
process_form_batch(
    "application_template.pdf",
    "submissions.json", 
    "completed_forms/"
)

from pypdf import PdfReader

def extract_form_data(pdf_path: str) -> dict:
    """Extract all form field values from a PDF."""
    
    reader = PdfReader(pdf_path)
    form_data = {}
    
    # Check if PDF has form fields
    if reader.is_encrypted:
        print("PDF is encrypted - decrypt first")
        return form_data
    
    try:
        # Access form fields through document structure
        if hasattr(reader, 'root_object') and '/AcroForm' in reader.root_object:
            acroform = reader.root_object['/AcroForm']
            if '/Fields' in acroform:
                fields = acroform['/Fields']
                for field_ref in fields:
                    field = field_ref.get_object()
                    if '/T' in field:  # Field name
                        field_name = field['/T']
                        field_value = field.get('/V', '')  # Field value
                        form_data[field_name] = field_value
    
    except Exception as e:
        print(f"Error extracting form data: {e}")
    
    return form_data

# Extract form data
data = extract_form_data("filled_form.pdf")
print("Form field values:", data)