--- title: TypedDict with extra items | daily.dev description: Python 3.15 adds an extra_items class parameter to TypedDict, letting you allow additional dictionary keys of a specified type. Setting extra_items=str on a... canonical: https://daily.dev/posts/typeddict-with-extra-items-y15hcfxfy twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: TypedDict with extra items | daily.dev og:description: Python 3.15 adds an extra_items class parameter to TypedDict, letting you allow additional dictionary keys of a specified type. Setting extra_items=str on a... og:url: https://daily.dev/posts/typeddict-with-extra-items-y15hcfxfy og:image: https://api.daily.dev/og/posts/Y15HCfxFY.png og:image:alt: TypedDict with extra items 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. # TypedDict with extra items **[Planet Python](https://daily.dev/sources/planetpython)** · 4 min read · 0 upvotes · 0 comments ## Summary Python 3.15 adds an extra_items class parameter to TypedDict, letting you allow additional dictionary keys of a specified type. Setting extra_items=str on a Movie TypedDict means an extra key like 'genre' with a string value still type checks, while a float value for an unknown key fails. A separate closed=True parameter locks a TypedDict to exactly its declared keys and blocks subclasses from adding more; it can't be combined with extra_items. The same extra_items setting also controls whether typing.Unpack allows extra keyword arguments in a function signature. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Questions this post answers ### How do I make a Python TypedDict allow extra keys with a specific type? Use the extra_items class parameter when defining the TypedDict, e.g. class Movie(TypedDict, extra_items=str). This lets dictionaries of that type include additional keys beyond those declared in the class body, as long as their values match the specified type. A key with a value of the wrong type still fails type checking. _Tracking new typing features like this gets easier when daily.dev surfaces Python 3.15 changes as they land._ ### What does closed=True do for a Python TypedDict? Setting closed=True on a TypedDict specifies that it has exactly the keys declared in its body and no others, and it also prevents subclasses from adding new keys. It cannot be combined with extra_items, and closed=False behaves the same as omitting both parameters, matching pre-3.15 TypedDict behavior. _Developers deciding how strict to make their type definitions can follow these typing changes on daily.dev._ ### How does extra_items affect typing.Unpack with keyword arguments in Python? When a TypedDict used with Unpack has no extra_items set, a function typed with Unpack accepts no extra keyword arguments beyond those declared. When extra_items=str is set, the function also accepts arbitrary extra keyword arguments of that type, equivalent to adding **kwargs: str to the signature manually. _Developers migrating function signatures to Python 3.15 typing features can keep up with these details on daily.dev._ ## Similar posts on daily.dev - [The varying strictness of TypedDict](https://daily.dev/posts/the-varying-strictness-of-typeddict-woau6xf94) · Planet Python · 0 upvotes · 0 comments - [Get started with Python’s new frozendict type](https://daily.dev/posts/get-started-with-python-s-new-frozendict-type-z3smdzvfm) · InfoWorld · 0 upvotes · 0 comments - [Python: store extra data for objects in a WeakKeyDictionary](https://daily.dev/posts/python-store-extra-data-for-objects-in-a-weakkeydictionary-i6dtgtava) · Adam Johnson · 0 upvotes · 0 comments - [The Joy of Typing](https://daily.dev/posts/the-joy-of-typing-r5aiqx2dz) · Towards Data Science · 0 upvotes · 0 comments --- Tags: [#general-programming](https://daily.dev/tags/general-programming), [#python](https://daily.dev/tags/python) [View this post on daily.dev](https://daily.dev/posts/typeddict-with-extra-items-y15hcfxfy) ```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":"TypedDict with extra items","url":"https://daily.dev/posts/typeddict-with-extra-items-y15hcfxfy","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/typeddict-with-extra-items-y15hcfxfy"},"datePublished":"2026-10-26T19:53:37.050Z","dateModified":"2026-10-26T19:57:22.820Z","description":"Python 3.15 adds an extra_items class parameter to TypedDict, letting you allow additional dictionary keys of a specified type. 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This lets dictionaries of that type include additional keys beyond those declared in the class body, as long as their values match the specified type. A key with a value of the wrong type still fails type checking. Tracking new typing features like this gets easier when daily.dev surfaces Python 3.15 changes as they land."}},{"@type":"Question","name":"What does closed=True do for a Python TypedDict?","acceptedAnswer":{"@type":"Answer","text":"Setting closed=True on a TypedDict specifies that it has exactly the keys declared in its body and no others, and it also prevents subclasses from adding new keys. It cannot be combined with extra_items, and closed=False behaves the same as omitting both parameters, matching pre-3.15 TypedDict behavior. 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