Sanity checks on Flask decorator

wrappers.py

from __future__ import print_function
from flask import Flask
from functools import wraps
import json
import sys

app = Flask(__name__)

def example_wrapper(f):
    print(f.func_dict)
    @wraps(f)
    def wrapped(*args, **kwargs):
        return json.dumps(f(*args, **kwargs))
    # Sanity check: make sure we're not already registered
    for endpoint, func in app.view_functions.iteritems():
        if func is f:
            print("Warning: wrapping already-registered endpoint '{}'; "
                  "are the decorators in the right order? (@app.route should be"
                  " the first).".format(endpoint), file=sys.stderr)
            break
    return wrapped

@example_wrapper
@app.route('/')
def eyes():
    return {'bees': 'faces'}

if __name__ == '__main__':
    app.run()