1811 words

9 minutes

Building a Markdown Blog Compiler with Python and Jinja2 Templates

2025-06-30

Project

Python

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Markdown

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Static Site

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Jinja2

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Blog

Building a Static Markdown Blog Compiler with Python and Jinja2#

A common approach for creating blogs involves dynamic server-side technologies or complex content management systems. An alternative gaining popularity is the static site approach, where content is pre-rendered into static HTML files. A Markdown blog compiler, using tools like Python and Jinja2, facilitates this process by transforming simple Markdown files into fully structured HTML pages. This method offers advantages such as speed, security, and simplified hosting.

The core idea is to automate the process of taking raw content (written in Markdown) and structural templates (defined using a templating engine like Jinja2) and combining them to produce ready-to-serve HTML files. This eliminates the need for server-side processing for each page view.

Essential Concepts#

Understanding a few key concepts is fundamental to building a Markdown blog compiler.

Markdown: A lightweight markup language with plain text formatting syntax. It is designed to be easily readable and writable, yet can be converted into structured formats like HTML. Markdown files are typically saved with a .md or .markdown extension.
Static Site: A website composed of pre-built HTML, CSS, and JavaScript files. Unlike dynamic sites that generate pages on demand using databases and server-side code, static sites serve files directly.
Compiler (in this context): Not a traditional code compiler, but a program or script that takes source files (like Markdown content and Jinja2 templates) and transforms them into a final output format, specifically static HTML files ready for deployment. This is essentially a form of static site generator.
Templating Engine: A tool that allows separating content from presentation. Templates define the structure and layout of a web page, with placeholders for dynamic content. A templating engine replaces these placeholders with actual data, producing the final output. Jinja2 is a popular and powerful templating engine for Python.
Python: A versatile programming language well-suited for scripting and automation tasks, including file system manipulation, text processing, and integrating libraries for Markdown conversion and templating.
File System Operations: The process involves reading input files (Markdown, templates, static assets) and writing output files (HTML, copied assets) to specific directories. Python’s built-in os and shutil modules are commonly used for these tasks.

Building a custom compiler provides flexibility, allowing tailored features and a deeper understanding of the static site generation process compared to using off-the-shelf generators.

Building the Markdown Blog Compiler: A Step-by-Step Walkthrough#

Constructing a basic Markdown blog compiler involves several stages, from setting up the project structure to processing files and rendering the final output.

Project Structure#

A clear directory structure organizes the input and output files. A typical layout might include:

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/project_root
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├── /content        # Markdown blog posts
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│   └── my-first-post.md
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│   └── another-post.md
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├── /templates      # Jinja2 templates
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│   └── base.html   # Base layout
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│   └── post.html   # Template for individual posts
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│   └── index.html  # Template for the index/homepage
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├── /static       # Static assets (CSS, JS, images)
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│   └── style.css
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├── compiler.py     # The Python script
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├── /output         # Generated static files (will be created)

This structure separates concerns: raw content in content, presentation logic in templates, static design elements in static, the build script at the root, and the final generated site in output.

Essential Libraries#

The core functionality relies on specific Python libraries:

markdown: For converting Markdown text to HTML. Install using pip: pip install python-markdown.
jinja2: For loading and rendering HTML templates. Install using pip: pip install Jinja2.
os: Python’s built-in module for interacting with the operating system, used for path manipulation, directory creation, and file listing.
shutil: Python’s built-in module for high-level file operations, used for copying directories (like the static assets).

Step-by-Step Implementation Logic#

The compiler.py script orchestrates the entire process.

1. Configuration and Setup#

Define input and output directories. Set up the Jinja2 environment.

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import os
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import shutil
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import markdown
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from jinja2 import Environment, FileSystemLoader
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# Define directories
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CONTENT_DIR = 'content'
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TEMPLATES_DIR = 'templates'
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STATIC_DIR = 'static'
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OUTPUT_DIR = 'output'
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# Set up Jinja2 environment
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# This tells Jinja2 where to find templates
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template_loader = FileSystemLoader(TEMPLATES_DIR)
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env = Environment(loader=template_loader)
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# Ensure output directory is clean
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if os.path.exists(OUTPUT_DIR):
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    shutil.rmtree(OUTPUT_DIR) # Remove existing output
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os.makedirs(OUTPUT_DIR) # Create new output directory
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os.makedirs(os.path.join(OUTPUT_DIR, CONTENT_DIR), exist_ok=True) # Create output content dir

This code initializes paths, sets up Jinja2 to look for templates in the templates directory, and prepares the output directory by clearing and recreating it. The nested directory inside output for content is prepared to mirror the input structure.

2. Copy Static Assets#

Copy the contents of the static directory directly to the output directory. Static files do not require processing.

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# Copy static files
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if os.path.exists(STATIC_DIR):
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    output_static_dir = os.path.join(OUTPUT_DIR, STATIC_DIR)
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    # Check if output_static_dir already exists from os.makedirs above
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    # If not, create it, then copy contents
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    if not os.path.exists(output_static_dir):
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         os.makedirs(output_static_dir)
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    # Use copytree to copy the directory and its contents
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    # Add dirs_exist_ok=True for Python 3.8+ or handle it manually
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    # For simplicity and compatibility, ensure target exists first then copy contents
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    # Alternative: shutil.copytree(STATIC_DIR, output_static_dir, dirs_exist_ok=True) # Requires Python 3.8+
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    # More compatible approach:
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    for item in os.listdir(STATIC_DIR):
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        s = os.path.join(STATIC_DIR, item)
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        d = os.path.join(output_static_dir, item)
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        if os.path.isdir(s):
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            shutil.copytree(s, d, dirs_exist_ok=True) # Use dirs_exist_ok if available or handle recursively
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        else:
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            shutil.copy2(s, d) # copy2 preserves metadata

Self-correction: shutil.copytree is simpler and usually creates the destination directory. A direct shutil.copytree(STATIC_DIR, os.path.join(OUTPUT_DIR, STATIC_DIR)) is more idiomatic, potentially adding dirs_exist_ok=True for robustness with pre-existing dirs (though we clear OUTPUT_DIR initially). Let’s simplify the copy part.

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# Copy static files more simply
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if os.path.exists(STATIC_DIR):
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    shutil.copytree(STATIC_DIR, os.path.join(OUTPUT_DIR, STATIC_DIR))

3. Process Markdown Files#

Iterate through the content directory, read each Markdown file, convert it to HTML, and extract metadata (if included).

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# Process content files
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posts_data = [] # Store data about each post for index page
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for root, _, files in os.walk(CONTENT_DIR):
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    for file in files:
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        if file.endswith('.md'):
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            filepath = os.path.join(root, file)
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            # Create corresponding output path (changing .md to .html)
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            relative_path = os.path.relpath(filepath, CONTENT_DIR)
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            output_filename = os.path.splitext(relative_path)[0] + '.html'
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            output_filepath = os.path.join(OUTPUT_DIR, CONTENT_DIR, output_filename)
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            # Ensure output directory for this file exists
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            os.makedirs(os.path.dirname(output_filepath), exist_ok=True)
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            # Read markdown content
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            with open(filepath, 'r', encoding='utf-8') as f:
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                content = f.read()
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            # Convert markdown to HTML
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            # Optionally use extensions for metadata
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            md = markdown.Markdown(extensions=['meta'])
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            html_content = md.convert(content)
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            metadata = md.Meta # Dictionary extracted by 'meta' extension
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            # --- Example: Extract title and date from metadata ---
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            title = metadata.get('title', ['Untitled Post'])[0]
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            date = metadata.get('date', ['No Date'])[0] # Example date format: YYYY-MM-DD
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            # Store post data for index page
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            # Output path is relative to the output directory for linking
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            link_path = os.path.join(CONTENT_DIR, output_filename)
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            posts_data.append({
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                'title': title,
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                'date': date,
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                'link': '/' + link_path.replace('\\', '/') # Use forward slashes for URLs
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            })
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            # --- Render post using Jinja2 template ---
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            post_template = env.get_template('post.html')
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            rendered_html = post_template.render(
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                title=title,
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                date=date,
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                content=html_content # Pass the converted HTML content
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            )
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            # Write the output HTML file
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            with open(output_filepath, 'w', encoding='utf-8') as f:
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                f.write(rendered_html)
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print(f"Processed {len(posts_data)} markdown files.")
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# Sort posts by date for index page (newest first)
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# Assuming date is in a sortable format like YYYY-MM-DD
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posts_data.sort(key=lambda x: x['date'], reverse=True)

This segment iterates through Markdown files, converts each to HTML, potentially extracts metadata using the meta Markdown extension, renders the content using a post.html Jinja2 template, and writes the resulting HTML to the output directory. It also collects data about each post to potentially build an index page later.

4. Generate Index Page#

Create an index page (e.g., index.html) listing the blog posts. This uses the data collected in the previous step.

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# Generate index page
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index_template = env.get_template('index.html')
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index_output_path = os.path.join(OUTPUT_DIR, 'index.html')
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rendered_index_html = index_template.render(
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    posts=posts_data # Pass the list of post data
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)
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with open(index_output_path, 'w', encoding='utf-8') as f:
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    f.write(rendered_index_html)
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print("Generated index page.")

This final step loads the index.html template, passes the sorted list of post data, and renders the main index page for the blog.

Example Files#

To illustrate the process, consider simple examples of the source files:

Example `content/my-first-post.md`#

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Title: My First Blog Post
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Date: 2023-10-27
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# Welcome!
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This is the content of my first blog post.
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It's written in **Markdown**.
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- Item 1
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- Item 2

Example `templates/base.html`#

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<!DOCTYPE html>
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<html lang="en">
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<head>
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    <meta charset="UTF-8">
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    <meta name="viewport" content="width=device-width, initial-scale=1.0">
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    <title>{% block title %}My Blog{% endblock %}</title>
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    <link rel="stylesheet" href="/static/style.css">
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</head>
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<body>
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    <header>
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        <h1>My Awesome Static Blog</h1>
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        <nav>
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            <a href="/">Home</a>
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        </nav>
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    </header>
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    <main>
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        {% block content %}{% endblock %}
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    </main>
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    <footer>
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        <p>&copy; 2023 My Blog</p>
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    </footer>
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</body>
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</html>

This base.html defines the overall structure and includes blocks ({% block ... %}) that child templates can override.

Example `templates/post.html`#

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{% extends "base.html" %}
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{% block title %}{{ title }} - My Blog{% endblock %}
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{% block content %}
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    <article>
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        <h2>{{ title }}</h2>
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        <p class="post-meta">Published on: {{ date }}</p>
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        <div class="post-content">
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            {{ content | safe }} {# 'safe' tells Jinja2 not to escape the HTML #}
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        </div>
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    </article>
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{% endblock %}

post.html extends base.html, sets the page title, and injects the post’s specific title, date, and the HTML-converted content into the content block. The | safe filter is crucial here because the content variable already holds HTML from the Markdown conversion; without safe, Jinja2 would escape the HTML tags.

Example `templates/index.html`#

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{% extends "base.html" %}
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{% block title %}Home - My Blog{% endblock %}
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{% block content %}
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    <h1>Blog Posts</h1>
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    <ul>
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        {% for post in posts %}
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            <li>
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                <a href="{{ post.link }}">{{ post.title }}</a>
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                <span class="post-date">({{ post.date }})</span>
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            </li>
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        {% end for %}
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    </ul>
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{% endblock %}

index.html also extends base.html and iterates through the posts list passed by the compiler script, creating a list of links to each post.

Example `static/style.css`#

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body {
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    font-family: sans-serif;
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    line-height: 1.6;
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    margin: 0 auto;
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    max-width: 800px;
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    padding: 20px;
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}
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header, footer {
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    text-align: center;
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    margin-bottom: 20px;
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}
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nav a {
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    margin: 0 10px;
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}
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article {
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    margin-bottom: 40px;
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}
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.post-meta {
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    font-size: 0.9em;
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    color: #555;
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}
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.post-content img {
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    max-width: 100%;
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    height: auto;
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}

A basic CSS file demonstrates how static assets are included.

Running the Compiler#

Execute the Python script from the project root:

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python compiler.py

This script will:

Clean and create the output directory.
Copy the static directory contents to output/static.
Read content/my-first-post.md.
Convert the Markdown to HTML.
Extract “My First Blog Post” and “2023-10-27” as metadata.
Render the HTML using templates/post.html.
Save the result as output/content/my-first-post.html.
Read content/another-post.md (if it existed) and repeat steps 3-7.
Render templates/index.html using the collected post data.
Save the result as output/index.html.

The output directory now contains a complete, static blog ready to be served by any web server.

Key Takeaways#

Building a Markdown blog compiler with Python and Jinja2 is a practical way to create static websites.
Static sites offer benefits such as enhanced performance, improved security, and lower hosting costs compared to dynamic alternatives.
Python’s markdown library converts Markdown content into HTML efficiently.
Jinja2 provides powerful and flexible templating capabilities to separate content from presentation and build structured HTML pages.
Structuring the project into content, templates, static, and output directories promotes organization and maintainability.
The compiler script orchestrates the process of reading input files, processing content, applying templates, and writing the final static output.
Metadata within Markdown files (using extensions like python-markdown’s meta) can be used to enrich templates with information like titles and dates.
Generating an index page requires collecting data from individual content files during the compilation process.

This custom compiler approach demonstrates the core mechanics of static site generation and offers a solid foundation for more complex features, such as categories, tags, pagination, or configuration files.