How to check for redundant combinations in a Python dictionary?

There will never be redundant combinations in a Python dictionary because it is a hashmap. This means that each key will have exactly one associated value with it. This value can be a list or another dict though. So if you try to add a duplicate key like

Example

a = {'foo': 42, 'bar': 55}
a['foo'] = 100
print(a)

Output

This will give the output

{'foo': 100, 'bar': 55}

If you really want multiple values for a single key, then you should probably use a list to be associated with the key and add values to that list.