Removes excessive empty lines from a Markdown file while preserving necessary structure

clean_markdown.py

import re
import sys

def clean_markdown(file_path, output_path=None):
    """
    Removes excessive empty lines from a Markdown file while preserving necessary structure.
    
    Args:
        file_path (str): Path to the input Markdown file.
        output_path (str, optional): Path to save the cleaned Markdown. If None, overwrites input file.
    """
    try:
        # Read the Markdown file
        with open(file_path, 'r', encoding='utf-8') as file:
            lines = file.readlines()

        # Strip trailing whitespace and normalize empty lines
        cleaned_lines = []
        previous_line_empty = False

        for line in lines:
            line = line.rstrip()  # Remove trailing whitespace and newlines

            # Skip completely empty lines (to process later)
            if not line:
                if not previous_line_empty:  # Only add one empty line
                    cleaned_lines.append("")
                previous_line_empty = True
                continue

            # Reset empty line flag if we encounter a non-empty line
            previous_line_empty = False

            # Preserve headers, lists, blockquotes, and other non-empty lines
            cleaned_lines.append(line)

        # Remove excessive empty lines while preserving single empty lines between content
        final_lines = []
        previous_line_empty = False

        for i, line in enumerate(cleaned_lines):
            is_empty = not line.strip()

            # Skip multiple consecutive empty lines
            if is_empty and previous_line_empty:
                continue

            # Preserve single empty lines between content for readability
            if is_empty and i > 0 and i < len(cleaned_lines) - 1:
                # Check if the next line is a header or list item to avoid unnecessary blank lines
                next_line = cleaned_lines[i + 1]
                if next_line.startswith('#') or re.match(r'^\s*[-*+]\s|\d+\.\s', next_line):
                    continue

            final_lines.append(line)
            previous_line_empty = is_empty

        # Remove trailing empty lines
        while final_lines and not final_lines[-1].strip():
            final_lines.pop()

        # Add a single newline at the end of the file
        final_lines.append("")

        # Determine output path
        output_file = output_path if output_path else file_path

        # Write the cleaned content back to the file
        with open(output_file, 'w', encoding='utf-8') as file:
            file.write('\n'.join(final_lines))

        print(f"Cleaned Markdown file saved to: {output_file}")

    except FileNotFoundError:
        print(f"Error: File '{file_path}' not found.")
    except Exception as e:
        print(f"An error occurred: {e}")

def main():
    if len(sys.argv) < 2:
        print("Usage: python clean_markdown.py <input_file> [output_file]")
        sys.exit(1)

    input_file = sys.argv[1]
    output_file = sys.argv[2] if len(sys.argv) > 2 else None
    clean_markdown(input_file, output_file)

if __name__ == "__main__":
    main()