How to iterate through a nested dict?

I have a nested python dictionary data structure. I want to read its keys and values without using collection module. The data structure is like bellow.

d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

I was trying to read the keys in the dictionary using the bellow way but getting error.

Code

for key, value in d:
    print(Key)

Error

ValueError: too many values to unpack (expected 2)

So can anyone please explain the reason behind the error and how to iterate through the dictionary.

As the requested output, the code goes like this

    d = {'dict1': {'foo': 1, 'bar': 2}, 'dict2': {'baz': 3, 'quux': 4}}

    for k1,v1 in d.iteritems(): # the basic way
        temp = ""   
        temp+=k1
        for k2,v2 in v1.iteritems():
           temp = temp+" "+str(k2)+" "+str(v2)
        print temp

In place of iteritems() you can use items() as well, but iteritems() is much more efficient and returns an iterator.

Hope this helps :)