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What are dictionaries and sets in Julia?

Joy Kareko

Overview

Dictionaries and sets are data structures in Julia. Data structures help us store data into computer memory in an organized way.

Dictionaries and sets have the below characteristics:

  • Dictionaries are organized in key-value pairs. Sets are not.
  • Keyword for a Dictionary is Dict() while set is Set().
  • Dictionaries and sets are both mutable. This means we can always alter, change, or delete the values specified.
  • They are both unordered. This means that values do not maintain the order in which they are specified. So, an item can appear last even if it was specified first.

Dictionaries

Syntax

Dictionary_name[key_name => value_name]
or
Dictionary_name[:key_name => value_name]

How to create a dictionary

The code below shows how to create a dictionary:

# Creating a dictionary
# The keys can either be strings or integers
data = Dict("a" => 1, "b" => 2, 1 => "Hello")
println(data)

data_2  = Dict(1 => 1, "ben" => 10)
println(data_2)

data_3 = Dict(:a => 1, :b => "one")
println(data_3)
Creating a dictionary

Accessing elements in a dictionary

We can access elements in a dictionary using keys or using the get() method as shown:

data = Dict("a" => 1, "b" => 2, 1 => "Hello")
#println(data)
println(data["a"])
println(data[1])

data_2  = Dict(1 => 1, "ben" => 10)
#print(data_2)
println(data_2["ben"])

data_3 = Dict(:a => 1, :b => "one")
println(data_3[:b])

Accessing elements of a dictionary

Using get() method

The syntax is as below:

get(Dictionary_name, Key_name, Default Value)

Example

data_3 = Dict("a" => 1, "b" => 2, 1 => "Hello")

println(get(data_3, "a", 0))

println(get(data_3,1,0))
Using the Get() method

Keys and values can be accessed in a similar way to the codes above.

The general syntax is:

Keys = keys(Dictionary_name)
Values = values(Dictionary_name)

Sets

Syntax

Below is the syntax for creating a set:

Setname = Set([Value1, Value2,....]) 

Creating and accessing elements of a set

#creating a set with integers only
Set1 = Set([1,2,3])
println(Set1)
# Creating a set with different datatypes
Set3 = Set([1, 2, 3, "Tom", "Chair"])
println(Set3)

#Accessing the elements
#Using a for loop
for i in Set1
    println(i)
end
Creating and accessing elements of a set

Note: Similar to the get() method in dictionaries, Julia has many methods used in dictionaries and sets. These methods help to add, delete, and manipulate the data further.

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