Dictionaries

Creating a Dictionary

We can create a dictionary using the following syntax:

D = Dict("a" => 1, "b" => 2, 1 => "a")

Alternatively, we can initialize a Dictionary using key/value pairs:

D = Dict([("a", 1), ("b", 2), (1,"a")])

Accessing Elements of a Dictionary

Elements of a dictionary can be accessed similarly to arrays, using the corresponding keys: for example, doing D["a"] or D[1] will return the corresponding values of 1 and "a".

Dictionaries are also iterable objects, so we can loop through the elements of a given dictionary:

for e in D
    println(e)
end

as each element in a dictionary is a Pair, we can access individual components of e doing e[1] and e[2]. More conveniently, we can unstructure the pair into two variables, as follows:

for (k,v) in D
    println(k, " => ", v)
end

b => 2
a => 1
1 => a

Modifying a Dictionary

One important characteristics of dictionaries is that they are mutable structures, so can be modified. For example, the following is possible:

D["c"] = 3           # Adding a new key
D["c"] = "Hello"     # Updating existing key
D = delete!(D, "c")  # Deleting an existing key