Python decorator access argument by name

You can use the inspect.getfullargspec() function to access the names used in a function:

try:    # Python 3    from inspect import getfullargspecexcept ImportError:    # Python 2, use inspect.getargspec instead    # this is the same function really, without support for annotations    # and keyword-only arguments    from inspect import getargspec as getfullargspecfrom functools import wrapsdef access_course_permission(argument_name):    def decorator(f):        argspec = getfullargspec(f)        argument_index = argspec.args.index(argument_name)        @wraps(f)        def wrapper(*args, **kwargs):            try:                value = args[argument_index]            except IndexError:                value = kwargs[argument_name]            # do something with value            return f(*args, **kwargs)        return wrapper    return decorator

The above finds out at what index your specific argument is positioned; this covers both positional and keyword arguments (because in Python, you can pass in a value for a keyword argument by position too).

Note however that for your specific example, Flask will call view_course with course_id as a keyword argument, so using kwargs[argument_name] would suffice.

You'll have to pass in a string to name that argument:

@app.route('/admin/courses/<int:course_id>')@access_course_permission('course_id')def view_course(course_id):    # ... view code here

Note however, that in Flask you could just access request.view_args, without the need to parse this information out of the function arguments:

course_id = requests.view_args[argument_name]