shtab 0.0.4

Automatically generate shell tab completion scripts for python CLI apps

• What: Automatically generate shell tab completion scripts for python CLI apps

• Why: Speed & correctness. Alternatives like argcomplete & 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 completion for bash and zsh

• Supports argparse and docopt (via argopt)

• Supports arguments, options and subparsers

• Supports path completion

Usage

Installing shtab’s own tab completion scripts is possible via:

# Install locally (eager)
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

# Install once (will have to re-run if the target's CLI API changes,
# but doesn't need target to always be in $PYTHONPATH)
shtab --shell=bash shtab.main.get_main_parser --error-unimportable \
  | sudo tee "$BASH_COMPLETION_COMPAT_DIR"/shtab

# zsh equivalent (alternatively place in $fpath/_shtab)
shtab --shell=zsh shtab.main.get_main_parser --error-unimportable \
  | sudo tee /usr/local/share/zsh/site-functions/_shtab

The same would work for most existing argparse-based scripts. For example, starting with this existing code:

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

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

Configuration

Alternatively, add direct support to scripts for a little more configurability:

import argparse
import shtab, os  # for completion magic

def get_main_parser():
    parser = argparse.ArgumentParser(prog="<MY_PROG>", ...)
    parser.add_argument("--install-completion-shell", choices=["bash", "zsh"])
    parser.add_argument(
        "--file",
        choices=shtab.Optional.FILE,  # file tab completion
    )
    parser.add_argument(
        "--dir",
        choices=shtab.Required.DIRECTORY,  # directory tab completion
        default=os.getenv("BASH_COMPLETION_USER_DIR"),
    )
    ...
    return parser

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

    # completion magic
    shell = args.install_completion_shell
    if shell:
        completion_script = shtab.complete(parser, shell=shell)
        filename = args.file or "<MY_PROG>"
        print("Writing to system completion directory...")
        with open(os.path.join(args.dir, filename), "w") as fd:
            fd.write(completion_script)
        print("Please restart your terminal.")

    ...

More Examples

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

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

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

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

    msg = "k thx bai!" if args.bye 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”)