How to warn about class (name) deprecation

Question

I have renamed a python class that is part of a library. I am willing to leave a possibility to use its previous name for some time but would like to warn user that it\'s de

Answer 1

Use inspect module to add placeholder for OldClass, then OldClsName is NewClsName check will pass, and a linter like pylint will inform this as error.

deprecate.py

import inspect
import warnings
from functools import wraps

def renamed(old_name):
    """Return decorator for renamed callable.

    Args:
        old_name (str): This name will still accessible,
            but call it will result a warn.

    Returns:
        decorator: this will do the setting about `old_name`
            in the caller's module namespace.
    """

    def _wrap(obj):
        assert callable(obj)

        def _warn():
            warnings.warn('Renamed: {} -> {}'
                        .format(old_name, obj.__name__),
                        DeprecationWarning, stacklevel=3)

        def _wrap_with_warn(func, is_inspect):
            @wraps(func)
            def _func(*args, **kwargs):
                if is_inspect:
                    # XXX: If use another name to call,
                    # you will not get the warning.
                    frame = inspect.currentframe().f_back
                    code = inspect.getframeinfo(frame).code_context
                    if [line for line in code
                            if old_name in line]:
                        _warn()
                else:
                    _warn()
                return func(*args, **kwargs)
            return _func

        # Make old name available.
        frame = inspect.currentframe().f_back
        assert old_name not in frame.f_globals, (
            'Name already in use.', old_name)

        if inspect.isclass(obj):
            obj.__init__ = _wrap_with_warn(obj.__init__, True)
            placeholder = obj
        else:
            placeholder = _wrap_with_warn(obj, False)

        frame.f_globals[old_name] = placeholder

        return obj

    return _wrap

test.py

from __future__ import print_function

from deprecate import renamed


@renamed('test1_old')
def test1():
    return 'test1'


@renamed('Test2_old')
class Test2(object):
    pass

    def __init__(self):
        self.data = 'test2_data'

    def method(self):
        return self.data

# pylint: disable=undefined-variable
# If not use this inline pylint option, 
# there will be E0602 for each old name.
assert(test1() == test1_old())
assert(Test2_old is Test2)
print('# Call new name')
print(Test2())
print('# Call old name')
print(Test2_old())

then run python -W all test.py:

test.py:22: DeprecationWarning: Renamed: test1_old -> test1
# Call new name
<__main__.Test2 object at 0x0000000007A147B8>
# Call old name
test.py:27: DeprecationWarning: Renamed: Test2_old -> Test2
<__main__.Test2 object at 0x0000000007A147B8>