Python decorator to allow use of f-strings in docstrings (something not normally supported by Python)

fmydocstrings.py

"""Simple decorator that applies f-string formatting to docstrings

To use, simply apply `@fmydocstring` to your function

Only global variables are accessible for interpolation.
"""

import functools


def fmydocstring(func):
    """Simple decorator to treat docstrings as f-strings"""
    func.__doc__ = eval(f'f"""{func.__doc__}"""',
                        globals()) if func.__doc__ is not None else None

    @functools.wraps(func)
    def func_wrapper(*args, **kwargs):
        return func(*args, **kwargs)

    return func_wrapper


# Try it out!
DESCRIPTION = "great!"


@fmydocstring
def my_cool_docstring():
    """My docstring is {DESCRIPTION}, also, {2+2=}
  
    Args: None
  
    Returns: None
    """
    ...


@fmydocstring
def no_docstring():
    # works correctly if there is no docstring
    ...


@fmydocstring
def empty_docstring():
    """"""
    # works fine on empty docstrings too
    ...


@fmydocstring
class Foo:
    """My class docstrings is {DESCRIPTION}
    
    Applying @fmydocstring to the class does not automatically decorate all class methods...yet
    """

    @fmydocstring
    def bar(self):
        """This is a {DESCRIPTION} class method"""


if __name__ == "__main__":
    print(my_cool_docstring.__doc__)
    assert (no_docstring.__doc__ is None)
    assert (empty_docstring.__doc__ == "")
    print(Foo.__doc__)
    print(Foo.bar.__doc__)

Play with this code in repl.it here