How to check if a variable is a dictionary in Python?

How would you check if a variable is a dictionary in Python?

For example, I’d like it to loop through the values in the dictionary until it finds a dictionary. Then, loop through the one it finds:

dict = {'abc': 'abc', 'def': {'ghi': 'ghi', 'jkl': 'jkl'}}
for k, v in dict.iteritems():
    if ###check if v is a dictionary:
        for k, v in v.iteritems():
            print(k, ' ', v)
    else:
        print(k, ' ', v)