Dictionaries are an incredibly powerful tool for making associative sets between two equal length lists. The first is a list of keys (or indexes) and the second – a set of values (or the data that will be returned for each index).

Inputs:

• keys: it must consist of unique strings or numbers.
• values: a value that will be returned for each key.
• search keys: the list of keys(indexes) that you want returned.

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The dictionary values can hold lists of objects:

Or Revit elements:

If a search key is not found in the dictionary, an empty list will be returned instead.