run once decorator

run_once.py

# from http://stackoverflow.com/questions/4103773/efficient-way-of-having-a-function-only-execute-once-in-a-loop
from functools import wraps
def run_once(f):
    """Runs a function (successfully) only once.

    The running can be reset by setting the `has_run` attribute to False
    """
    @wraps(f)
    def wrapper(*args, **kwargs):
        if not wrapper.has_run:
            result = f(*args, **kwargs)
            wrapper.has_run = True
            return result
    wrapper.has_run = False
    return wrapper

@run_once
def load_ipython_extension(ip):
    """Load the extension in IPython."""
    # do work
    pass

it has something wrong when reload or restart app

@wraps(f)
    def wrapper(*args, **kwargs):
        if not f.has_run:
            result = f(*args, **kwargs)
            f.has_run = True
            return result
    f.has_run = False
    return wrapper