Iterate through Python dictionary by Keys in sorted order [duplicate]

Question

I have a dictionary in Python that looks like this:

D = {1:'a', 5:'b', 2:'a', 7:'a'} 

The values of the keys are mostly irrelevant. Is there are way to iterate through the dictionary by keys in numerical order? The keys are all integers.

Instead of saying

for key in D:     # some code... 

Can I go through the dictionary keys in the order 1, 2, 5, 7?

Additionally, I cannot use the sort/sorted functions.

Answer 1

You can use this:

for key in sorted(D.iterkeys()):     .. code .. 

In Python 3.x, use D.keys() (which is the same as D.iterkeys() in Python 2.x).