# render_block and Def Scope

URL: /docs/troubleshooting/render-block-scope/
Section: troubleshooting
Tags: troubleshooting, render_block, def, blocks

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render_block and Def Scope When you call template.render_block(&quot;block_name&quot;, context), the block is rendered in isolation. It does not have access to &#123;% def %&#125; macros defined in the same template. The Problem {# page.html — def and block in same file #} &#123;% def helper() %&#125;shared logic&#123;% end %&#125; &#123;% block content %&#125; {{ helper() }} {# NameError or UndefinedError when using render_block #} &#123;% end %&#125; If a framework (e.g. Chirp) calls template.render_block(&quot;content&quot;, ...), the block cannot see helper because blocks are compiled with their own scope. Fix Split defs into a separate file and import them: {# _helpers.html #} &#123;% def helper() %&#125;shared logic&#123;% end %&#125; {# page.html #} &#123;% from &quot;_helpers.html&quot; import helper %&#125; &#123;% block content %&#125; {{ helper() }} &#123;% end %&#125; Now both full-page render() and render_block(&quot;content&quot;, ...) work, because the block imports helper from another template. When This Matters Fragment rendering — Chirp and similar frameworks use render_block() to return HTML fragments for htmx, SSE, etc. Block caching — Site-scoped block caching renders blocks individually via render_block(). See Also Functions and macros — &#123;% def %&#125; and &#123;% from %&#125; Block caching — Caching individual blocks

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