Wolfram Language & System Documentation Center

JSONLines (.jsonl)

See Also
- Import
- Export
- CloudExport
- CloudImport
- Formats
- ArrowIPC
- Parquet
- ORC
- ArrowDataset
- CSV
- RawJSON
- JSON
Related Guides
- See Also
  - Import
  - Export
  - CloudExport
  - CloudImport
  - Formats
  - ArrowIPC
  - Parquet
  - ORC
  - ArrowDataset
  - CSV
  - RawJSON
  - JSON
- Related Guides

JSONLines (.jsonl)

Import and Export support the JSONLines file format.

Background & Context

- Registered MIME types: application/jsonl
- JSON Lines data format.
- Consists of multiple JSON objects, one per line, representing individual data rows.
- Commonly used for storing structured JSON data.
- Text file format.

Import & Export

Import ["file.jsonl"] imports a JSONLines file as a Tabular object.
Import ["file.jsonl",elem] imports the specified elements.
Import ["file.jsonl",{elem,subelem₁,…}] imports subelements subelem_i, useful for partial data import.
The import format can be specified with Import ["file","JSONL"] or Import ["file",{"JSONL",elem,…}].
Export ["file.jsonl",expr] creates a JSONLines file from expr.
Supported expressions expr include:
{v₁,v₂,…} a single column of data

{{v₁₁,v₁₂,…},{v₂₁,v₂₂,…},…} lists of rows of data

array an array such as SparseArray , QuantityArray , etc.

tseries a TimeSeries , EventSeries or a TemporalData object

dataset a Dataset or a Tabular object
See the following reference pages for full general information:
Import , Export import from or export to a file

CloudImport , CloudExport import from or export to a cloud object

ImportString , ExportString import from or export to a string

ImportByteArray , ExportByteArray import from or export to a byte array

Import Elements

General Import elements:
"Elements" list of elements and options available in this file

"Summary" summary of the file

"Rules" list of rules for all available elements
Data representation elements:
"Data" two-dimensional array

"Dataset" table data as a Dataset

"EventSeries" table data as an EventSeries

"Tabular" a Tabular object

"TimeSeries" table data as a TimeSeries
Import by default uses the "Tabular" element.
Subelements for partial data import for the "Tabular" element can take row and column specifications in the form {"Tabular",rows,cols}, where rows and cols can be any of the following:
n n^th row or column

-n counts from the end

n;;m from n through m

n;;m;;s from n through m with steps of s

{n₁,n₂,…} specific rows or columns n_i
Column specifications can also be any of the following:
"col" single column "col"

{col₁,col₂,…} list of column names col_i
Data descriptor elements:
"ColumnLabels" names of columns

"ColumnTypes" association with data type for each column

"Schema" TabularSchema object
Metadata elements:
"ColumnCount" number of columns stored in file

"Dimensions" data dimensions

"RowCount" number of rows stored in file

"MetaInformation" metadata

Import Options

General Import options:
"BlockSize" 1048576 how many bytes to process at a time

"Schema" Automatic schema used to construct Tabular object

"TimeColumn" Automatic column to use for times in "EventSeries" and "TimeSeries" elements
Possible settings for the "Schema" option include:
schema a complete TabularSchema specification

propval a schema property and value (see reference page for TabularSchema )

<|"prop₁"val₁,…|> an association of schema properties and values

Export Options

Export options include:
"ExpressionFormattingFunction" Automatic how expressions stored in a Tabular object are converted to strings
"ExpressionFormattingFunction" can be set to the following values:
Automatic default conversion to string

form any form supported by Format such as InputForm

f arbitrary function that converts an expression to a string

Examples

open all close all

Basic Examples (3)

Import Tabular object from JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl"]

Import the file summary:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Summary"]

Export Tabular object to JSONLines file:

Wolfram Language code: tabular = Import["ExampleData/world_cups.jsonl"];

Wolfram Language code: Export["file.jsonl", tabular]

Scope (3)

Import (3)

Show all elements available in the file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Elements"]

By default, a Tabular object is returned:

Wolfram Language code: Import["ExampleData/world_cups.jsonl"]//TabularQ

Import column types:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "ColumnTypes"]

Import Elements (18)

"ColumnCount" (1)

Get the number of columns:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "ColumnCount"]

"ColumnLabels" (1)

Read column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "ColumnLabels"]

"ColumnTypes" (1)

Import column types:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "ColumnTypes"]

"Data" (3)

Get the data from a file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Data"]

Import only selected rows:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Data", 1 ;; 2}]

Import only selected columns:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Data", All, {1, 2}}]

Import selected columns using column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Data", All, {"Year", "Host Country"}}]

"Dataset" (3)

Get the data as a Dataset :

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Dataset"]

Import only selected rows:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Dataset", 1 ;; 2}]

Import only selected columns:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Dataset", All, {1, 2}}]

Import selected columns using column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Dataset", All, {"Year", "Host Country"}}]

"Dimensions" (1)

Import data dimensions:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Dimensions"]

"EventSeries" (1)

Import a JSONLines file as an EventSeries :

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "EventSeries"]

Import a single row from a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"EventSeries", 5}]

Import some specific rows from a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"EventSeries", {1, 5, 7}}]

Import the first 10 rows of a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"EventSeries", 1 ;; 10}]

Import only selected columns using column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"EventSeries", All, {"Year", "Host Country", "Winner"}}]

"RowCount" (1)

Get the number of rows:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "RowCount"]

"Schema" (1)

Get the TabularSchema object:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Schema"]

"Summary" (1)

Get the file summary:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Summary"]

"Tabular" (3)

Get the data from a file as a Tabular object:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "Tabular"]

Import only selected rows:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Tabular", 1 ;; 2}]

Import only selected columns:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Tabular", All, {1, 2}}]

Import selected columns using column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"Tabular", All, {"Year", "Host Country"}}]

"TimeSeries" (1)

Import a JSONLines file as a TimeSeries :

Wolfram Language code: Import["ExampleData/world_cups.jsonl", "TimeSeries"]

Import a single row from a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"TimeSeries", 5}]

Import some specific rows from a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"TimeSeries", {1, 5, 7}}]

Import the first 10 rows of a JSONLines file:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"TimeSeries", 1 ;; 10}]

Import only selected columns using column names:

Wolfram Language code: Import["ExampleData/world_cups.jsonl", {"TimeSeries", All, {"Year", "Host Country", "Winner"}}]

Import Options (3)

"BlockSize" (1)

Create a JSONLines file:

Wolfram Language code: Export["trees.jsonl", ResourceData["Sample Tabular Data: NYC Trees"]];

Import data using the default setting of "BlockSize"->2^20:

Wolfram Language code: RepeatedTiming[Import["trees.jsonl"];]

Import data faster by specifying the value of the "BlockSize" option:

Wolfram Language code: AssociationMap[First@RepeatedTiming[Import["trees.jsonl", "BlockSize" -> 2 ^ #];]&, {19, 21, 22}]

"Schema" (1)

Wolfram Language code:

file = Export["out.jsonl", Tabular[Association["RawSchema" -> Association["ColumnProperties" -> 
 Association["A" -> Association["ElementType" -> "String"], 
 "B" -> Association["ElementType" -> "String"]], "KeyColumns" -> None, 
 "Backend" -> "WolframKernel"], "BackendData" -> 
 Association["ColumnData" -> DataStructure["ColumnTable", 
 {{TabularColumn[Association["Data" -> {{0, {0, 11, 22, 33, 44, 55}, 
 "Jan 03 2006Jan 04 2006Jan 05 2006Jan 06 2006Jan 09 2006"}, {}, None}, 
 "ElementType" -> "String"]], TabularColumn[Association[
 "Data" -> {{3, {0, 5, 10, 15, 20, 25}, "11.8212.0412.0911.8812.43"}, {}, None}, 
 "ElementType" -> "String"]]}}]]]]];

By default, column labels and their types stored in a file are used when Tabular or Dataset objects are imported:

Wolfram Language code:

tabular = Import[file];
tabular["ColumnTypes"]

Use the "Schema" option to specify column labels and types:

Wolfram Language code:

tabular = Import[file, "Schema" -> {"ColumnKeys" -> {"Date", "Value"}, "ElementType" -> {"Date" -> "Date", "Value" -> "Real32"}}]

"TimeColumn" (1)

Export a Tabular object to a JSONLines file:

Wolfram Language code:

file = Export["file.jsonl", Tabular[Association["RawSchema" -> Association["ColumnProperties" -> 
 Association["Date" -> Association["ElementType" -> TypeSpecifier["Date"]["Integer32", "Day", 
 "Gregorian", None]], "Value" -> Association["ElementType" -> "Real32"]], 
 "KeyColumns" -> None, "Backend" -> "WolframKernel"], "Options" -> {}, 
 "BackendData" -> Association["ColumnData" -> DataStructure["ColumnTable", 
 {{TabularColumn[Association["Data" -> {5, {{NumericArray[{13150, 13151, 13152, 13153, 13156}, 
 "Integer32"], {}, None}}, None}, "ElementType" -> "Date"["Integer32", "Day", 
 "Gregorian", None]]], TabularColumn[Association[
 "Data" -> {NumericArray[{11.819999694824219, 12.039999961853027, 12.09000015258789, 
 11.880000114440918, 12.430000305175781}, "Real32"], {}, None}, 
 "ElementType" -> "Real32"]]}}]]]]];

By default, the time column is selected automatically for "TimeSeries" and "EventSeries" elements:

Wolfram Language code: Import[file, "TimeSeries"]

Use the "TimeColumn" option to specify the time column:

Wolfram Language code: Import[file, "TimeSeries", "TimeColumn" -> "Value"]

Export Options (1)

"ExpressionFormattingFunction" (1)

By default, Export uses different conversion to string depending on column types:

Wolfram Language code: tabular = Import["ExampleData/USstates.arrow", {"Tabular", 1 ;; 3}]

Wolfram Language code: ColumnTypes[tabular]

Wolfram Language code: ExportString[tabular, "JSONLines"]

Use "ExpressionFormattingFunction"->InputForm to get string versions of expressions suitable for input to the Wolfram Language:

Wolfram Language code: ExportString[tabular, "JSONLInes", "ExpressionFormattingFunction" -> InputForm]//Short[#, 5]&

Use an arbitrary function such as SpokenString :

Wolfram Language code: ExportString[tabular, "JSONLines", "ExpressionFormattingFunction" -> SpokenString]

Use a function that specifies different rules for different expression types:

Wolfram Language code:

Clear[f]
f[x_Image] := ImageIdentify[x];
f[x_] := ToString[x, OutputForm]

Wolfram Language code: ExportString[tabular, "JSONLines", "ExpressionFormattingFunction" -> f]

Applications (1)

Import a large JSONLines file from Kaggle:

Wolfram Language code:

data = DataConnectionObject[<|"ConnectionName" -> "Kaggle", "Location" -> "https://www.kaggle.com/datasets/devdope/900k-spotify?select=900k+Definitive+Spotify+Dataset.json"|>];

Wolfram Language code: Import[data, "JSONLines"]

Wolfram Language code: Dimensions[%]