CSV v2.3.1 CSV View Source

RFC 4180 compliant CSV parsing and encoding for Elixir. Allows to specify other separators, so it could also be named: TSV, but it isn't.

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Functions

Decode a stream of comma-separated lines into a stream of tuples. Decoding errors will be inlined into the stream

Decode a stream of comma-separated lines into a stream of tuples. Errors when decoding will get raised immediately

Encode a table stream into a stream of RFC 4180 compliant CSV lines for writing to a file or other IO

Link to this section Functions

Link to this function

decode(stream, options \\ []) View Source

Decode a stream of comma-separated lines into a stream of tuples. Decoding errors will be inlined into the stream.

Options

These are the options:

  • :separator – The separator token to use, defaults to ?,. Must be a codepoint (syntax: ? + (your separator)).
  • :strip_fields – When set to true, will strip whitespace from cells. Defaults to false.
  • :preprocessor – Which preprocessor to use: :lines (default) -> Will preprocess line by line input respecting escape sequences :none -> Will not preprocess input and expects line by line input with multiple line escape sequences aggregated to one line
  • :validate_row_length – If set to false, will disable validation for row length. This will allow for rows with variable length. Defaults to true

    • :escape_max_lines – How many lines to maximally aggregate for multiline escapes. Defaults to a 1000.
    • :num_workers – The number of parallel operations to run when producing the stream.
    • :worker_work_ratio – The available work per worker, defaults to 5. Higher rates will mean more work sharing, but might also lead to work fragmentation slowing down the queues.
    • :headers – When set to true, will take the first row of the csv and use it as header values. When set to a list, will use the given list as header values. When set to false (default), will use no header values. When set to anything but false, the resulting rows in the matrix will be maps instead of lists.

Examples

Convert a filestream into a stream of rows in order of the given stream:

iex> "../test/fixtures/docs/valid.csv"
iex> |> Path.expand(__DIR__)
iex> |> File.stream!
iex> |> CSV.decode
iex> |> Enum.take(2)
[ok: ["a","b","c"], ok: ["d","e","f"]]

Errors will show up as error tuples:

iex> "../test/fixtures/docs/escape-errors.csv"
iex> |> Path.expand(__DIR__)
iex> |> File.stream!
iex> |> CSV.decode
iex> |> Enum.take(2)
[
  ok: ["a","b","c"],
  error: "Escape sequence started on line 2 near \"d,e,f\n\" did not terminate.\n\nEscape sequences are allowed to span up to 1000 lines. This threshold avoids collecting the whole file into memory when an escape sequence does not terminate. You can change it using the escape_max_lines option: https://hexdocs.pm/csv/CSV.html#decode/2"
]

Map an existing stream of lines separated by a token to a stream of rows with a header row:

iex> ["a;b","c;d", "e;f"]
iex> |> Stream.map(&(&1))
iex> |> CSV.decode(separator: ?;, headers: true)
iex> |> Enum.take(2)
[
  ok: %{"a" => "c", "b" => "d"},
  ok: %{"a" => "e", "b" => "f"}
]

Map an existing stream of lines separated by a token to a stream of rows with a given header row:

iex> ["a;b","c;d", "e;f"]
iex> |> Stream.map(&(&1))
iex> |> CSV.decode(separator: ?;, headers: [:x, :y])
iex> |> Enum.take(2)
[
  ok: %{:x => "a", :y => "b"},
  ok: %{:x => "c", :y => "d"}
]
Link to this function

decode!(stream, options \\ []) View Source

Decode a stream of comma-separated lines into a stream of tuples. Errors when decoding will get raised immediately.

Options

These are the options:

  • :separator – The separator token to use, defaults to ?,. Must be a codepoint (syntax: ? + (your separator)).
  • :strip_fields – When set to true, will strip whitespace from cells. Defaults to false.
  • :preprocessor – Which preprocessor to use: :lines (default) -> Will preprocess line by line input respecting escape sequences :none -> Will not preprocess input and expects line by line input with multiple line escape sequences aggregated to one line
  • :escape_max_lines – How many lines to maximally aggregate for multiline escapes. Defaults to a 1000.
  • :validate_row_length – If set to false, will disable validation for row length. This will allow for rows with variable length. Defaults to true
  • :num_workers – The number of parallel operations to run when producing the stream.
  • :worker_work_ratio – The available work per worker, defaults to 5. Higher rates will mean more work sharing, but might also lead to work fragmentation slowing down the queues.
  • :headers – When set to true, will take the first row of the csv and use it as header values. When set to a list, will use the given list as header values. When set to false (default), will use no header values. When set to anything but false, the resulting rows in the matrix will be maps instead of lists.

Examples

Convert a filestream into a stream of rows in order of the given stream:

iex> "../test/fixtures/docs/valid.csv"
iex> |> Path.expand(__DIR__)
iex> |> File.stream!
iex> |> CSV.decode!
iex> |> Enum.take(2)
[["a","b","c"], ["d","e","f"]]

Errors will be raised:

iex> "../test/fixtures/docs/row-length-errors.csv"
iex> |> Path.expand(__DIR__)
iex> |> File.stream!
iex> |> CSV.decode!
iex> |> Enum.take(2)
** (CSV.RowLengthError) Row has length 3 - expected length 2 on line 2

Map an existing stream of lines separated by a token to a stream of rows with a header row:

iex> ["a;b","c;d", "e;f"]
iex> |> Stream.map(&(&1))
iex> |> CSV.decode!(separator: ?;, headers: true)
iex> |> Enum.take(2)
[
  %{"a" => "c", "b" => "d"},
  %{"a" => "e", "b" => "f"}
]

Map an existing stream of lines separated by a token to a stream of rows with a given header row:

iex> ["a;b","c;d", "e;f"]
iex> |> Stream.map(&(&1))
iex> |> CSV.decode!(separator: ?;, headers: [:x, :y])
iex> |> Enum.take(2)
[
  %{:x => "a", :y => "b"},
  %{:x => "c", :y => "d"}
]
Link to this function

encode(stream, options \\ []) View Source

Encode a table stream into a stream of RFC 4180 compliant CSV lines for writing to a file or other IO.

Options

These are the options:

  • :separator – The separator token to use, defaults to ?,. Must be a codepoint (syntax: ? + (your separator)).
  • :delimiter – The delimiter token to use, defaults to \r\n. Must be a string.

Examples

Convert a stream of rows with cells into a stream of lines:

iex> [~w(a b), ~w(c d)]
iex> |> CSV.encode
iex> |> Enum.take(2)
["a,b\r\n", "c,d\r\n"]

Convert a stream of rows with cells with escape sequences into a stream of lines:

iex> [["a\nb", "\tc"], ["de", "\tf\""]]
iex> |> CSV.encode(separator: ?\t, delimiter: "\n")
iex> |> Enum.take(2)
["\"a\\nb\"\t\"\\tc\"\n", "de\t\"\\tf\"\"\"\n"]