Docx template filling

docx-template-filling

Overview

This skill provides a robust framework for filling Microsoft Word templates using the python-docx library. It specifically addresses the "Split Placeholder" problem and supports conditional content blocks.

Core Principles

1. Paragraph-Level Processing: Always modify text at the paragraph level (para.text) rather than the run level (run.text) to avoid issues where Word splits placeholders like {{NAME}} into multiple runs (e.g., {{NA and ME}}).
2. Formatting Preservation: When replacing text in a paragraph, clear all runs except the first one. Update the first run's text to the new content to preserve the paragraph's initial formatting.
3. Comprehensive Traversal: Process the main document body, tables (including nested ones), and headers/footers of all sections.

Handling Conditional Sections

Conditional sections are marked with {{IF_CONDITION}}...{{END_IF_CONDITION}}.

• If condition is True: Remove the markers but keep the content in between.
• If condition is False: Remove the entire block including markers and content.

Implementation Pattern for Conditionals

def process_conditionals(doc, condition_key, is_enabled):
    start_marker = f"{{{{IF_{condition_key}}}}}"
    end_marker = f"{{{{END_IF_{condition_key}}}}}"
    
    # Track paragraphs to delete if condition is False
    paras_to_delete = []
    in_block = False
    
    for para in doc.paragraphs:
        if start_marker in para.text:
            in_block = True
            # Remove marker from this paragraph
            para.text = para.text.replace(start_marker, "")
        
        if in_block and not is_enabled:
            paras_to_delete.append(para)
            
        if end_marker in para.text:
            in_block = False
            # Remove marker from this paragraph
            para.text = para.text.replace(end_marker, "")

Handling Split Placeholders

Use a regex-based replacement strategy at the paragraph level.

import re

def replace_placeholders(para, data):
    text = para.text
    pattern = r"\{\{([A-Z_0-9]+)\}\}"
    matches = re.findall(pattern, text)
    
    if not matches:
        return False
        
    new_text = text
    for key in matches:
        placeholder = f"{{{{{key}}}}}"
        if key in data:
            new_text = new_text.replace(placeholder, str(data[key]))
            
    if new_text != text:
        # Preserve first run formatting
        if para.runs:
            para.runs[0].text = new_text
            for run in para.runs[1:]:
                run.text = ""
        else:
            para.text = new_text
        return True
    return False

Traversal Logic

Ensure all parts of the document are reached:

• doc.paragraphs
• doc.tables (recurse into cell.paragraphs and cell.tables)
• doc.sections (iterate section.header.paragraphs and section.footer.paragraphs)