hajs / shtab

↔️ Automagic shell tab completion for Python CLI applications

shtab

• What: Automatically generate shell tab completion scripts for python CLI apps
• Why: Speed & correctness. Alternatives like argcomplete and pyzshcomplete are slow and have side-effects
• How: shtab processes an argparse.ArgumentParser object to generate a tab completion script for your shell

Features

• Outputs tab completion scripts for
  • bash
  • zsh
• Supports
  • argparse
  • docopt (via argopt)
• Supports arguments, options and subparsers
• Supports choices (e.g. --say={hello,goodbye})
• Supports file and directory path completion
• Supports custom path completion (e.g. --file={*.txt})

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Table of Contents

• shtab
  • Features
  • Installation
    • Ubuntu/Debian
    • MacOS
  • Usage
    • bash
      • Eager bash
    • zsh
      • Eager zsh
  • Examples
  • FAQs
  • Advanced Configuration
    • docopt
  • Alternatives
  • Contributions

Installation

Choose one of:

• pip install shtab
• conda install -c conda-forge shtab

bash users who have never used any kind of tab completion before should also follow the OS-specific instructions below.

Ubuntu/Debian

Recent versions should have completion already enabled. For older versions, first run sudo apt install --reinstall bash-completion, then make sure these lines appear in ~/.bashrc:

# enable bash completion in interactive shells
if ! shopt -oq posix; then
 if [ -f /usr/share/bash-completion/bash_completion ]; then
   . /usr/share/bash-completion/bash_completion
 elif [ -f /etc/bash_completion ]; then
   . /etc/bash_completion
 fi
fi

MacOS

First run brew install bash-completion, then add the following to ~/.bash_profile:

if [ -f $(brew --prefix)/etc/bash_completion ]; then
   . $(brew --prefix)/etc/bash_completion
fi

Usage

The only requirement is that external CLI applications provide an importable argparse.ArgumentParser object (or alternatively an importable function which returns a parser object). This may require a trivial code change.

Once that's done, simply put the output of shtab --shell=your_shell your_cli_app.your_parser_object somewhere your shell looks for completions.

Below are various examples of enabling shtab's own tab completion scripts.

bash

shtab --shell=bash shtab.main.get_main_parser --error-unimportable \
  | sudo tee "$BASH_COMPLETION_COMPAT_DIR"/shtab

Eager bash

If both shtab and the module it's completing are globally importable, eager usage is an option. "Eager" means automatically updating completions each time a terminal is opened.

# Install locally
echo 'eval "$(shtab --shell=bash shtab.main.get_main_parser)"' \
  >> ~/.bash_completion

# Install locally (lazy load for bash-completion>=2.8)
echo 'eval "$(shtab --shell=bash shtab.main.get_main_parser)"' \
  > "${BASH_COMPLETION_USER_DIR:-${XDG_DATA_HOME:-$HOME/.local/share}/bash-completion}/completions/shtab"

# Install system-wide
echo 'eval "$(shtab --shell=bash shtab.main.get_main_parser)"' \
  | sudo tee "$(pkg-config --variable=completionsdir bash-completion)"/shtab

# Install system-wide (legacy)
echo 'eval "$(shtab --shell=bash shtab.main.get_main_parser)"' \
  | sudo tee "$BASH_COMPLETION_COMPAT_DIR"/shtab

zsh

Note that zsh requires completion script files to be named _{EXECUTABLE} (with an underscore prefix).

# note the underscore `_` prefix
shtab --shell=zsh shtab.main.get_main_parser --error-unimportable \
  | sudo tee /usr/local/share/zsh/site-functions/_shtab

Eager zsh

To be more eager, place the generated script somewhere in $fpath. For example, add these lines to the top of ~/.zshrc:

mkdir -p ~/.zsh/completions
fpath=($fpath ~/.zsh/completions)  # must be before `compinit` lines
shtab --shell=zsh shtab.main.get_main_parser > ~/.zsh/completions/_shtab

Examples

See the examples/ folder for more.

Any existing argparse-based scripts should be supported with minimal effort. For example, starting with this existing code:

#!/usr/bin/env python
import argparse

def get_main_parser():
    parser = argparse.ArgumentParser(prog="MY_PROG", ...)
    parser.add_argument(...)
    parser.add_subparsers(...)
    ...
    return parser

if __name__ == "__main__":
    parser = get_main_parser()
    args = parser.parse_args()
    ...

Assuming this code example is installed in MY_PROG.command.main, simply run:

# bash
shtab --shell=bash -u MY_PROG.command.main.get_main_parser \
  | sudo tee "$BASH_COMPLETION_COMPAT_DIR"/MY_PROG

# zsh
shtab --shell=zsh -u MY_PROG.command.main.get_main_parser \
  | sudo tee /usr/local/share/zsh/site-functions/_MY_PROG

FAQs

Not working? Make sure that shtab and the application you're trying to complete are both accessible from your environment.

"Eager" installation (completions are re-generated upon login/terminal start) is recommended. Naturally, shtab and the CLI application to complete should be accessible/importable from the login environment. If installing shtab in a different virtual environment, you'd have to add a line somewhere appropriate (e.g. $CONDA_PREFIX/etc/conda/activate.d/env_vars.sh).

By default, shtab will silently do nothing if it cannot import the requested application. Use -u, --error-unimportable to noisily complain.

Advanced Configuration

See the examples/ folder for more.

Complex projects with subparsers and custom completions for paths matching certain patterns (e.g. --file=*.txt) are fully supported (see iterative/dvc:command/completion.py for example).

Add direct support to scripts for a little more configurability:

#!/usr/bin/env python
import argparse
import shtab  # for completion magic

def get_main_parser():
    parser = argparse.ArgumentParser(prog="pathcomplete")
    parser.add_argument(
        "-s",
        "--print-completion-shell",
        choices=["bash", "zsh"],
        help="prints completion script",
    )
    # file & directory tab complete
    parser.add_argument("file", nargs="?").complete = shtab.FILE
    parser.add_argument("--dir", default=".").complete = shtab.DIRECTORY
    return parser

if __name__ == "__main__":
    parser = get_main_parser()
    args = parser.parse_args()

    # completion magic
    shell = args.print_completion_shell
    if shell:
        print(shtab.complete(parser, shell=shell))
    else:
        print("received <file>=%r --dir=%r" % (args.file, args.dir))

docopt

Simply use argopt to create a parser object from docopt syntax:

#!/usr/bin/env python
"""Greetings and partings.

Usage:
  greeter [options] [<you>] [<me>]

Options:
  -g, --goodbye  : Say "goodbye" (instead of "hello")
  -b, --print-bash-completion  : Output a bash tab-completion script
  -z, --print-zsh-completion  : Output a zsh tab-completion script

Arguments:
  <you>  : Your name [default: Anon]
  <me>  : My name [default: Casper]
"""
import sys, argopt, shtab  # NOQA

parser = argopt.argopt(__doc__)
if __name__ == "__main__":
    args = parser.parse_args()
    if args.print_bash_completion:
        print(shtab.complete(parser, shell="bash"))
        sys.exit(0)
    if args.print_zsh_completion:
        print(shtab.complete(parser, shell="zsh"))
        sys.exit(0)

    msg = "k thx bai!" if args.goodbye else "hai!"
    print("{} says '{}' to {}".format(args.me, msg, args.you))

Alternatives

• argcomplete
  • executes the underlying script every time <TAB> is pressed (slow and has side-effects)
  • only provides bash completion
• pyzshcomplete
  • executes the underlying script every time <TAB> is pressed (slow and has side-effects)
  • only provides zsh completion
• click
  • different framework completely replacing argparse
  • solves multiple problems (rather than POSIX-style "do one thing well")

Contributions

Please do open issues & pull requests! Some ideas:

• support fish
• support powershell
• support tcsh

See CONTRIBUTING.md for more guidance.