scala-circe-json

name	scala-circe-json
description	Guide for using Circe in Scala 2.13 for parsing and generating JSON, specifically when translating Python JSON handling.

Using Circe for JSON in Scala 2.13

When converting Python's json module usage (e.g., json.loads, json.dumps, JsonValue = Union[...]), Scala relies on the Circe library. Since Scala 2.13 does not support native union types, JSON trees are best represented using the io.circe.Json Algebraic Data Type (ADT).

Setup

Ensure Circe dependencies are available.

import io.circe._
import io.circe.parser._
import io.circe.syntax._

Basic Operations

Parsing JSON (like json.loads)

In Python:

import json
data = json.loads('{"key":"value"}')

In Scala:

val jsonString = """{"key":"value"}"""
val jsonAst = parse(jsonString).getOrElse(Json.Null)

Serializing JSON (like json.dumps)

In Python:

json.dumps(data)
json.dumps(data, indent=2)

In Scala:

val compactStr = jsonAst.noSpaces
val prettyStr = jsonAst.spaces2

Navigating JSON Trees

Python uses dict/list indexing:

value = data.get("key")[0]

In Scala, use Cursors or pattern matching on Json methods:

val valueOption = jsonAst.hcursor.downField("key").downArray.focus
// or traversing Json values directly:
val objOption: Option[JsonObject] = jsonAst.asObject
val arrOption: Option[Vector[Json]] = jsonAst.asArray