Mako
Fast Python templating engine — compiles templates to Python for high-performance rendering. Mako features: ${expression} syntax for variable output, <%! %> for module-level code, <% %> for Python code blocks, ${func()} for function calls, def/block for reusable components, inheritance via <%inherit file='base.html'/>, <%include file='other.html'/> for includes, caching support, unicode-safe rendering, TemplateLookup for file-based templates, Template() for string templates, strict_undefined for error on missing variables, and default='' for safe missing values. Default template engine for Pyramid web framework.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
CRITICAL: Mako templates execute arbitrary Python — NEVER render user-controlled templates. No auto-escaping by default — XSS vulnerability if rendering user content without | h filter. Use strict_undefined=True to catch missing variable bugs. Mako maintained by SQLAlchemy team — good security track record. For user-facing templates with untrusted content, use Jinja2 SandboxedEnvironment instead.
⚡ Reliability
Best When
High-performance Python templating with full Python syntax in templates — Mako's compilation to Python makes it faster than Jinja2 for complex templates, and its Python-in-template syntax is familiar to Python developers.
Avoid When
User-controlled templates (security risk — executes Python), Jinja2-based ecosystems, or when sandboxing is required.
Use Cases
- • Agent HTML generation — from mako.template import Template; tmpl = Template('''<html><body><h1>${title}</h1>% for item in items:<p>${item.name}: ${item.value}</p>% endfor</body></html>'''); output = tmpl.render(title='Report', items=data) — render HTML with loops; agent generates HTML reports from data
- • Agent file template lookup — from mako.lookup import TemplateLookup; lookup = TemplateLookup(directories=['/agent/templates']); tmpl = lookup.get_template('report.html'); output = tmpl.render(**context) — file-based templates; agent loads templates from directory; TemplateLookup caches compiled templates for performance
- • Agent code generation — tmpl = Template('''class ${class_name}: % for method in methods: def ${method.name}(self${', ' + ', '.join(method.args) if method.args else ''}): ${method.body} % endfor'''); code = tmpl.render(class_name='Agent', methods=spec) — Python code generation; agent generates boilerplate code from specs; Mako's Python-in-template makes complex logic natural
- • Agent template inheritance — base.html: <html><%block name='content'/></html>; page.html: <%inherit file='base.html'/><%block name='content'>${page_body}</%block> — template inheritance; agent generates consistent HTML with shared layout; child templates override blocks
- • Agent string template — from mako.template import Template; msg_tmpl = Template('Agent ${name} completed ${task_count} tasks in ${duration:.1f}s'); msg = msg_tmpl.render(name='alpha', task_count=42, duration=3.14) — simple string rendering; agent notification messages with variable substitution
Not For
- • Security-critical user templates — Mako executes Python in templates; never render user-controlled template strings
- • Jinja2 ecosystem — many frameworks expect Jinja2; for Jinja2 use jinja2 library
- • Non-HTML templates with strict sandboxing — Mako has no sandbox; for sandboxed templates use Jinja2 with SandboxedEnvironment
Interface
Authentication
No auth — local templating library.
Pricing
Mako is MIT licensed. Free for all use.
Agent Metadata
Known Gotchas
- ⚠ Templates execute arbitrary Python — NEVER render user-controlled template strings; Template(user_input).render() executes Python code; agent accepting template from external source must never use Mako directly; use Jinja2 SandboxedEnvironment for user templates; Mako has no sandbox mode
- ⚠ Output not auto-escaped — ${user_content} does not HTML-escape; agent generating HTML from user data must: ${user_content | h} (Mako built-in h filter) or: from markupsafe import escape; ${escape(content)}; un-escaped user content causes XSS vulnerability
- ⚠ strict_undefined=True recommended for debugging — by default, undefined variables render as empty string; agent code with typo in variable name silently produces wrong output; TemplateLookup(strict_undefined=True) raises NameError on undefined; add for development, may need exception handling for optional variables in production
- ⚠ Mako vs Jinja2 syntax difference — Mako: ${var} and % for x in y:; Jinja2: {{ var }} and {% for x in y %}; agent developers switching between frameworks make syntax errors; Mako uses Python for loops (% for x in items:) ending with % endfor; indentation not significant unlike Python
- ⚠ Template inheritance requires TemplateLookup — <%inherit file='base.html'/> only works with TemplateLookup, not Template(); Template() has no file system access; agent code using inheritance must use TemplateLookup(directories=[...]); direct Template() for string templates without inheritance
- ⚠ mako.exceptions.RichTraceback for error diagnosis — template errors produce confusing Python tracebacks pointing to compiled code; from mako import exceptions; try: tmpl.render(**ctx); except: print(exceptions.text_error_template().render()) — shows template-aware traceback with Mako source line numbers instead of compiled Python
Alternatives
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Scores are editorial opinions as of 2026-03-06.