Indexing Python dictionaries with tuples

In Python it is possible to index dictionaries with tuples.

I made use of this technique in one of my previous posts, covering constraint programming with Google OR-tools in Python.

I demonstrate the technique in the coding example below:

# declare empty dictionary
dictObj = {}
# adding elements, indexed (keyed) with a tuple
for i in range(3):
    for j in range(3):
        dictObj[(i,j)] = i + j
# print dictionary content
print(dictObj)
{(0, 0): 0, (0, 1): 1, (0, 2): 2, (1, 0): 1, (1, 1): 2, (1, 2): 3, (2, 0): 2, (2, 1): 3, (2, 2): 4}

This technique is especially helpful when combined with list comprehensions in Python. See my post on job scheduling with Google OR-Tools and constraint programming in Python for a more sophisticated coding example.

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