# List Commands

One of the most common patterns with command line programs is the need to print lists of data. cliff provides a base class for commands of this type so that they only need to prepare the data, and the user can choose from one of several output formatter plugins to see the list of data in their preferred format.

## Lister

The `cliff.lister.Lister` base class API extends `Command` to allow `take_action()` to return data to be formatted using a user-selectable formatter. Subclasses should provide a `take_action()` implementation that returns a two member tuple containing a tuple with the names of the columns in the dataset and an iterable that will yield the data to be output. See the description of the files command in the demoapp for details.

## List Output Formatters

cliff is delivered with two output formatters for list commands. `Lister` adds a command line switch to let the user specify the formatter they want, so you don’t have to do any extra work in your application.

### csv

The `csv` formatter produces a comma-separated-values document as output. CSV data can be imported into a database or spreadsheet for further manipulation.

    (.venv)$ cliffdemo files -f csv
    "Name","Size"
    "build",136
    "cliffdemo.log",2690
    "Makefile",5569
    "source",408

### table

The `table` formatter uses PrettyTable to produce output formatted for human consumption.

    (.venv)$ cliffdemo files
    +---------------+------+
    |      Name     | Size |
    +---------------+------+
    | build         |  136 |
    | cliffdemo.log | 2546 |
    | Makefile      | 5569 |
    | source        |  408 |
    +---------------+------+

### value

The `value` formatter produces a space separated output with no headers.

    (.venv)$ cliffdemo files -f value
    build 136
    cliffdemo.log 2690
    Makefile 5569
    source 408

This format can be very convenient when you want to pipe the output to a script.

    (.venv)$ cliffdemo files -f value | while read NAME SIZE
    do
      echo $NAME is $SIZE bytes
    done
    build is 136 bytes
    cliffdemo.log is 2690 bytes
    Makefile is 5569 bytes
    source is 408 bytes

### yaml

The `yaml` formatter uses PyYAML to produce a YAML sequence of mappings.

    (.venv)$ cliffdemo files -f yaml
    - Name: dist
      Size: 4096
    - Name: cliffdemo.egg-info
      Size: 4096
    - Name: README.rst
      Size: 960
    - Name: setup.py
      Size: 1807
    - Name: build
      Size: 4096
    - Name: cliffdemo
      Size: 4096

### json

The `json` formatter produces an array of objects in indented JSON format.

    (.venv)$ cliffdemo files -f json
    [
      {
        "Name": "source",
        "Size": 4096
      },
      {
        "Name": "Makefile",
        "Size": 5569
      },
      {
        "Name": "build",
        "Size": 4096
      }
    ]

### Other Formatters

A formatter using tablib to produce HTML is available as part of cliff-tablib.

### Creating Your Own Formatter

If the standard formatters do not meet your needs, you can bundle another formatter with your program by subclassing from `cliff.formatters.base.ListFormatter` and registering the plugin in the `cliff.formatter.list` namespace.

this page last updated: 2026-02-20 17:00:00

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