Associations can have arbitrary expressions as keys, including associations:

Append to an association:

Associations work with any number of elements:

Extracting values from an association is highly efficient:

Missing elements are represented by Missing:

Lookup allows a default value to be given:

Extract a value from an association using Part:

Extract a portion of the value:

The Key[k] part specification works at any level whose value is an association:

Extract the third value in an association:

Extract the value associated with the key 3:

Obtain the sub-association consisting of the second and third parts of an association:

Use the keys 2 and 3 instead:

Extract the value associated with the key {2,3}:

Extract a value using Extract:

Obtain the value without letting it evaluate:

Separate an association into a list of keys and a list of values:

Convert it to a list of ordered pairs:

Associations can be used for pattern matching:

Extract key and value from an association:

Replace arguments of a function:

Pick the rule with the specific key:

Filter associations with length 2 only:

Define a function using an association as an argument:

Use nested associations as a function argument:

KeyValuePattern lets you match any element in an association:

KeyValuePattern matches elements that appear anywhere in an association: