Define what an object can DO, not what it IS. A class doesn't need to inherit from a Protocol — it just needs to match the shape. Like TypeScript interfaces with `implements` optional.
Python
from typing import Protocol
class Closeable(Protocol):
def close(self) -> None: ...
def safe_use(resource: Closeable) -> None:
try:
# ... do work
pass
finally:
resource.close()
class File:
def close(self): print("file closed")
class Connection:
def close(self): print("conn closed")
safe_use(File()) # ✓ — has close()
safe_use(Connection()) # ✓ — has close()
# safe_use("hello") # mypy error — str has no close()Save your own code snippets
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