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How to Emit Deprecation Warnings in Python

Use the warnings module to mark legacy classes and methods as deprecated, letting users know to switch to newer APIs.

import warnings


class OldAPI:
    def __init__(self):
        warnings.warn(
            "OldAPI is deprecated; use NewAPI instead.",
            DeprecationWarning,
            stacklevel=2,
        )
        self.data = []

    def add(self, item):
        warnings.warn(
            "OldAPI.add() is deprecated; us…

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