Complaint about @staticmethod outside a class

[gvanrossum]

I found code like this:

def foo():
    @staticmethod
    def bar():
        pass

This gets an error:

/Users/guido/mypy_tests/mypy_static.py: note: In function "foo":
/Users/guido/mypy_tests/mypy_static.py:2: error: 'staticmethod' used with a non-method

It can be silenced by putting # type: ignore on the @staticmethod line.

[JukkaL]

What's the purpose of that code? Does it return the function?

[refi64]

I think this is probably to add static methods to a class dynamically? Like:

MyClass.bar = bar

[gvanrossum]

The pattern is like this:

    def _create_accessor(col):
        @staticmethod  # type: ignore
        def fn(row):
            try:
                return row[col]
            except (KeyError, IndexError):
                return None
        return fn

    _get_updated_host_id = _create_accessor('updated_host_id')
    _get_local_host_id = _create_accessor('local_host_id')

(and lots more like those last two lines).