Getting keys that were updated with the using a dictionaries update method

Is it possible to get the keys that where changed when using the update method?

def func(**kw):
    d = {'key0' : 0, 'key1' : 1}
    d.update(**kw)

func(kw0=0, kw1=1)

In the above code I'd want to get the key开发者_运维问答s 'kw0' and 'kw1'.

---

No, once update() is called, they are indistinguishable from the other keys.

Inside the function you can still look at kw.keys() to see which ones were passed in

eg

def func(**kw):
    d = {'key0' : 0, 'key1' : 1}
    d.update(**kw)
    print "updated %s"%kw.keys()

func(kw0=0, kw1=1)

---

The only way to detect the keys that were changed, is to store a copy of original dict, and then compare updated version, and original version.

def func(**kw):
    d = {'key0' : 0, 'key1' : 1}
    old = dict(d)
    d.update(kw)
    changed_keys = [key for key in d if old.get(key) != d.get(key)]
    print changed_keys