Question

Consider the following code fragment.

def print_timing(func):
    import time
    def wrapper(*args, **kwargs):
        t1 = time.time()
        res = func(*args, **kwargs)
        t2 = time.time()
        print '%s took %0.3f s ~ %0.0f min and %0.1f sec' % (func.func_name, t2-t1, int(t2 - t1)/60, (t2-t1) % 60 )
        return res
    return wrapper

@print_timing                                                                      |
def foo():                                                                         |
    return 'foo' 

class name(object):
       def __init__(self, name):
              self.name = name
       @print_timing
       def __call__(self):
              return self.name

bar = name("bar")
print bar()

This returns:

__call__ took 0.000 s ~ 0 min and 0.0 sec
bar

The object bar behaves like a function called bar, but exposes the internal implementation detail of __call__ when used with the decorator print_timing. Is there a way to change the name object (perhaps by passing a suitable argument to the __init__ function) so it returns instead

 bar took 0.000 s ~ 0 min and 0.0 sec

? I want a solution that will let the print_timing decorator continue to work with ordinary functions. Running
print foo() gives

foo took 0.000 s ~ 0 min and 0.0 sec
foo

Answer 1

As long as you use the decorator only on methods, they’ll be passed self as the first argument:

def print_timing(func):
    import time
    def wrapper(*args, **kwargs):
        t1 = time.time()
        res = func(*args, **kwargs)
        t2 = time.time()
        funcname = func.__name__
        # Special case; a "name" instance has a "name" attribute we want to use instead.
        if len(args) >= 1 and isinstance(args[0], name):
            funcname = args[0].name
        print '%s took %0.3f s ~ %0.0f min and %0.1f sec' % (funcname, t2-t1, int(t2 - t1)/60, (t2-t1) % 60 )
        return res
    return wrapper

Updated: The wrapper now uses func.__name__ by default, but if you use this on a name class (as in your original question), it’ll use the name attribute of the instance instead.

I’ve used an isinstance test to determine that a name attribute will be present, but you could use duck-typing instead (if hasattr(args[0], 'name')); the name variable is so generic however that you most likely will get unexpected results when used on arbitrary class methods.