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Title: `isinstance` on `runtime_checkable` `Protocol` has side-effects for `@property` methods · Issue #102433 · python/cpython · GitHub

Open Graph Title: `isinstance` on `runtime_checkable` `Protocol` has side-effects for `@property` methods · Issue #102433 · python/cpython

X Title: `isinstance` on `runtime_checkable` `Protocol` has side-effects for `@property` methods · Issue #102433 · python/cpython

Description: For example: from typing import Protocol, runtime_checkable @runtime_checkable class X(Protocol): @property def myproperty(self): ... class Y: @property def myproperty(self): raise RuntimeError("hallo") isinstance(Y(), X) will raise the ...

Open Graph Description: For example: from typing import Protocol, runtime_checkable @runtime_checkable class X(Protocol): @property def myproperty(self): ... class Y: @property def myproperty(self): raise RuntimeError("ha...

X Description: For example: from typing import Protocol, runtime_checkable @runtime_checkable class X(Protocol): @property def myproperty(self): ... class Y: @property def myproperty(self): raise RuntimeError(&qu...

Opengraph URL: https://github.com/python/cpython/issues/102433

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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"`isinstance` on `runtime_checkable` `Protocol` has side-effects for `@property` methods","articleBody":"For example:\r\n\r\n```python\r\nfrom typing import Protocol, runtime_checkable\r\n\r\n@runtime_checkable\r\nclass X(Protocol):\r\n   @property\r\n   def myproperty(self): ...\r\n\r\nclass Y:\r\n   @property\r\n   def myproperty(self):\r\n      raise RuntimeError(\"hallo\")\r\n\r\nisinstance(Y(), X)\r\n```\r\n\r\nwill raise the `RuntimeError`\r\n\r\nThis is an issue, for example, if `myproperty` is an expensive call, has unwanted side effects, or excepts outside of a context manager\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-102449\n* gh-102592\n* gh-102593\n* gh-103034\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/chrisjsewell","@type":"Person","name":"chrisjsewell"},"datePublished":"2023-03-05T03:46:05.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":29},"url":"https://github.com/102433/cpython/issues/102433"}

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