# Error Handling

URL: /docs/usage/error-handling/
Section: usage
Tags: usage, debugging

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Error Handling Kida provides clear error messages with source locations. Exception Types Exception When Raised TemplateError Base class for all template errors TemplateSyntaxError Invalid template syntax TemplateNotFoundError Template file not found UndefinedError Accessing undefined variable Syntax Errors from kida import Environment, TemplateSyntaxError env = Environment() try: template = env.from_string("{% if x %}") # Missing end except TemplateSyntaxError as e: print(e) # TemplateSyntaxError: Unexpected end of template (expected {% end %}) # File "<string>", line 1 Error messages include: Error description File name (or <string> for from_string) Line number Relevant source snippet Undefined Variables By default, undefined variables raise UndefinedError: from kida import UndefinedError template = env.from_string("{{ missing }}") try: html = template.render() except UndefinedError as e: print(e) # UndefinedError: Undefined variable 'missing' in <string>:1 Handle Missing Values Use the default filter: {{ user.nickname | default("Anonymous") }} {{ config.timeout | default(30) }} Or check with is defined: {% if user is defined %} {{ user.name }} {% end %} Template Not Found from kida import TemplateNotFoundError try: template = env.get_template("nonexistent.html") except TemplateNotFoundError as e: print(e) # TemplateNotFoundError: Template 'nonexistent.html' not found in: templates/ Runtime Errors Python errors during rendering include template context: template = env.from_string("{{ items[10] }}") try: html = template.render(items=[1, 2, 3]) except IndexError as e: # Traceback shows template location pass Debug Filter Inspect values during development: {{ posts | debug }} {{ posts | debug("my posts") }} Output (to stderr): DEBUG [my posts]: <list[5]> [0] Post(title='First Post', weight=10) [1] Post(title='Second', weight=None) <-- None: weight ... Common Error Patterns Missing Variable UndefinedError: Undefined variable 'usre' in page.html:5 Fix: Check for typos, ensure variable is passed to render(). Attribute Error UndefinedError: 'dict' object has no attribute 'nmae' Fix: Check attribute spelling, verify object type. Type Error in Filter TypeError: object of type 'NoneType' has no len() Fix: Use default filter or check for None. {{ items | default([]) | length }} Template Not Found TemplateNotFoundError: Template 'bsae.html' not found Fix: Check file path, verify loader configuration. Error Handling in Production from kida import TemplateError def render_page(template_name, **context): try: return env.render(template_name, **context) except TemplateError as e: # Log error logger.error(f"Template error: {e}") # Return fallback return env.render("error.html", error=str(e)) Best Practices Validate Context def render_safely(template, **context): # Validate required fields required = ["title", "user"] missing = [k for k in required if k not in context] if missing: raise ValueError(f"Missing context: {missing}") return template.render(**context) Use Default Values {# Defensive defaults #} {{ user.name | default("Guest") }} {{ items | default([]) | length }} {{ config.get("timeout", 30) }} Check Before Access {% if user and user.profile %} {{ user.profile.bio }} {% end %} See Also Undefined Variable — Debug undefined errors Template Not Found — Fix loading issues API Reference — Exception classes

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