Simple Rate Limiter Decorator for Python

ratellimit.py

import time

def rate_limit(sec: float = 0):
    """Rate limit a function by number of seconds between calls.
    
    Rate is time passage aware so if the last call was over the limiter, then the next call will be immediate.
    Additionally if the time past since the last call was half the time limit, then the next call will be delayed
    by half the time limit.
    
    ### Examples:
    ```python
    >>> @rate_limit(2)
    ... def foo():
    ...     print("bar")
    ... 
    >>> foo()
    bar
    >>> foo()
    bar

    """
    last_call = None
    def decorator(func):
        def wrapper(*args, **kwargs):
            nonlocal last_call
            if last_call is not None:
                time_since_last_call = time.time() - last_call
                if time_since_last_call < sec:
                    time.sleep(sec - time_since_last_call)
            last_call = time.time()
            return func(*args, **kwargs)
        return wrapper
    return decorator

def _test():
    import doctest
    doctest.testmod()

if __name__ == "__main__":
    _test()

I did some tests, it appears to be thread-safe... neat.