95 – Docstring __doc__ attribute

Docstrings are saved as an attribute __doc__ on the objects they were defined in. (Both functions and classes.)

This __doc__ is a string attribute that is both readable and writable. This is used by the built-in help, by functools.wraps in decorators, and more.

As an example, consider the function fn with a short docstring:

def fn():
    """Docstring!"""

If you use the built-in help, you’ll see the docstring:

help(fn)
"""
fn()
    Docstring!
"""

You can read and write to this attribute:

print(fn.__doc__)  # Docstring!
fn.__doc__ = "Bye!"

Then, things like the built-in help will see the new value for the docstring:

help(fn)
"""
fn()
    Bye!
"""