Work with dictionaries

A dictionary type is a collection of key-value pairs with keys of the same type and values of the same type.

• Dictionary syntax
• Reference dictionary values
• Operate on dictionaries

Dictionary syntax

A dictionary literal contains a set of key-value pairs (also known as elements) enclosed in square brackets ([]). Elements are comma-delimited. Keys must all be the same type. Values must all be the same type. Keys are associated to values by a colon (:).

Example dictionaries

[0: "Sun", 1: "Mon", 2: "Tue"]

["red": "#FF0000", "green": "#00FF00", "blue": "#0000FF"]

[1.0: {stable: 12, latest: 12}, 1.1: {stable: 3, latest: 15}]

Reference dictionary values

Flux dictionaries are key-indexed. To reference values in a dictionary:

1. Import the dict package.

2. Use dict.get() and provide the following parameters:

   • dict: Dictionary to reference
   • key: Key to reference
   • default: Default value to return if the key does not exist

import "dict"

positions =
    [
        "Manager": "Jane Doe",
        "Asst. Manager": "Jack Smith",
        "Clerk": "John Doe",
    ]

dict.get(dict: positions, key: "Manager", default: "Unknown position")
// Returns Jane Doe

dict.get(dict: positions, key: "Teller", default: "Unknown position")
// Returns Unknown position

Operate on dictionaries

• Create a dictionary from a list
• Insert a key-value pair into a dictionary
• Remove a key-value pair from a dictionary
• Return the string representation of a dictionary
• Include the string representation of a dictionary in a table

Create a dictionary from a list

1. Import the dict package.
2. Use dict.fromList() to create a dictionary from an array of records. Each record must have a key and value property.

import "dict"

list = [{key: "k1", value: "v1"}, {key: "k2", value: "v2"}]

dict.fromList(pairs: list)
// Returns [k1: v1, k2: v2]

Insert a key-value pair into a dictionary

1. Import the dict package.
2. Use dict.insert() to insert a key-value pair into a dictionary. If the key already exists, it’s overwritten with the new value.

import "dict"

exampleDict = ["k1": "v1", "k2": "v2"]

dict.insert(dict: exampleDict, key: "k3", value: "v3")
// Returns [k1: v1, k2: v2, k3: v3]

Remove a key-value pair from a dictionary

1. Import the dict package.
2. Use dict.remove() to remove a key-value pair from a dictionary.

import "dict"

exampleDict = ["k1": "v1", "k2": "v2"]

dict.remove(dict: exampleDict, key: "k2")
// Returns [k1: v1]

Return the string representation of a dictionary

Use display() to return Flux literal representation of a dictionary as a string.

x = ["a": 1, "b": 2, "c": 3]

display(v: x)

// Returns "[a: 1, b: 2, c: 3]"

Include the string representation of a dictionary in a table

Use display() to return Flux literal representation of a dictionary as a string and include it as a column value.

import "sampledata"

sampledata.string()
    |> map(fn: (r) => ({_time: r._time, exampleDict: display(v: ["tag": r.tag, "value":r._value])}))

Output