--- title: CPython doesn’t execute your .py file directly | daily.dev description: CPython compiles Python source files to bytecode before execution, even when no .pyc file is written. The .pyc files in __pycache__ are just cached bytecode... canonical: https://daily.dev/posts/cpython-doesn-t-execute-your-py-file-directly-iodqx5ugs twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: CPython doesn’t execute your .py file directly | daily.dev og:description: CPython compiles Python source files to bytecode before execution, even when no .pyc file is written. The .pyc files in __pycache__ are just cached bytecode... og:url: https://daily.dev/posts/cpython-doesn-t-execute-your-py-file-directly-iodqx5ugs og:image: https://api.daily.dev/og/posts/iODqX5UGS.png og:image:alt: CPython doesn’t execute your .py file directly og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # CPython doesn’t execute your .py file directly **[Medium](https://daily.dev/sources/medium_js)** · 2 min read · 0 upvotes · 0 comments ## Summary CPython compiles Python source files to bytecode before execution, even when no .pyc file is written. The .pyc files in __pycache__ are just cached bytecode for imported modules — not for directly-run scripts, since those only execute once. The cache filename encodes the interpreter version, and CPython validates it using file timestamps, size, or optionally a hash. Using dis.dis() reveals that even simple Python expressions compile into multiple bytecode instructions, which is a key reason CPython is slower than natively compiled languages like C — operations are resolved at runtime through Python's object model rather than compiled to fixed machine instructions. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [Write C Code Without Learning C: The Magic of PythoC](https://daily.dev/posts/write-c-code-without-learning-c-the-magic-of-pythoc-woxahty0c) · Towards Data Science · 0 upvotes · 0 comments - [Speed-up Native Python Code using Cython](https://daily.dev/posts/speed-up-native-python-code-using-cython-chjwtqj9o) · Daily Dose of Data Science \| Avi Chawla \| Substack · 5 upvotes · 0 comments - [PythoC: A new way to generate C code from Python](https://daily.dev/posts/pythoc-a-new-way-to-generate-c-code-from-python-hhhyci0hl) · InfoWorld · 2 upvotes · 0 comments --- Tags: [#python](https://daily.dev/tags/python), [#cpython](https://daily.dev/tags/cpython) [View this post on daily.dev](https://daily.dev/posts/cpython-doesn-t-execute-your-py-file-directly-iodqx5ugs) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"CPython doesn’t execute your .py file directly","url":"https://daily.dev/posts/cpython-doesn-t-execute-your-py-file-directly-iodqx5ugs","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/cpython-doesn-t-execute-your-py-file-directly-iodqx5ugs"},"datePublished":"2026-07-06T05:35:54.144Z","dateModified":"2026-07-06T05:37:07.514Z","description":"CPython compiles Python source files to bytecode before execution, even when no .pyc file is written. 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