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JSONLines (.jsonl)

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.arrow",{elem,subelem1,…}] imports subelements subelemi, 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
    arrayan array such as SparseArray, QuantityArray, etc.
    dataseta Dataset or a Tabular object
  • See the following reference pages for full general information:
  • Import, Exportimport from or export to a file
    CloudImport, CloudExportimport from or export to a cloud object
    ImportString, ExportStringimport from or export to a string
    ImportByteArray, ExportByteArrayimport 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
    "Tabular"a Tabular object
  • 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:
  • nnth row or column
    -ncounts from the end
    n;;mfrom n through m
    n;;m;;sfrom n through m with steps of s
    {n1,n2,…}specific rows or columns ni
  • 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"1048576how many bytes to process at a time
    "Schema"Automaticschema used to construct Tabular object
  • Possible settings for the "Schema" option include:
  • schemaa complete TabularSchema specification
    propvala schema property and value (see reference page for TabularSchema)
    <|"prop1"val1,…|>an association of schema properties and values
  • Possible settings for the "UnexpectedFieldBehavior" option include:
  • "InferType"unexpected JSON fields are type-inferred and included in the output
    "Error"unexpected JSON fields cause an error
    "Ignore"unexpected JSON fields are ignored

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:
  • Automaticdefault conversion to string
    formany form supported by Format such as InputForm
    farbitrary function that converts an expression to a string

Examples

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Basic Examples  (3)

Import Tabular object from JSONLines file:

Import the file summary:

Export Tabular object to JSONLines file:

Scope  (3)

Import  (3)

Show all elements available in the file:

By default, a Tabular object is returned:

Import column types:

Import Elements  (13)

"ColumnCount"  (1)

Get the number of columns:

"ColumnLabels"  (1)

Read column names:

"ColumnTypes"  (1)

Import column types:

"Data"  (2)

Get the data from a file:

Import only selected rows:

Import only selected columns:

"Dataset"  (2)

Get the data as a Dataset:

Import only selected rows:

Import only selected columns:

"Dimensions"  (1)

Import data dimensions:

"RowCount"  (1)

Get the number of rows:

"Schema"  (1)

Get the TabularSchema object:

"Summary"  (1)

Get the file summary:

"Tabular"  (2)

Get the data from a file as a Tabular object:

Import only selected rows:

Import only selected columns:

Import Options  (2)

"BlockSize"  (1)

Create a JSONLines file:

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

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

"Schema"  (1)

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

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

Export Options  (1)

"ExpressionFormattingFunction"  (1)

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

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

Use an arbitrary function such as SpokenString:

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

Applications  (1)

Import a large JSONLines file from Kaggle: