Bash tab completion for argparse
Project description
Tab complete all the things!
Argcomplete provides easy, extensible command line tab completion of arguments for your Python script.
It makes two assumptions:
You’re using bash or zsh as your shell
You’re using argparse to manage your command line arguments/options
Argcomplete is particularly useful if your program has lots of options or subparsers, and if your program can dynamically suggest completions for your argument/option values (for example, if the user is browsing resources over the network).
Installation
pip install argcomplete activate-global-python-argcomplete
See Activating global completion below for details about the second step (or if it reports an error).
Refresh your bash environment (start a new shell or source /etc/profile).
Synopsis
Python code (e.g. my-awesome-script.py):
#!/usr/bin/env python
# PYTHON_ARGCOMPLETE_OK
import argcomplete, argparse
parser = argparse.ArgumentParser()
...
argcomplete.autocomplete(parser)
args = parser.parse_args()
...Shellcode (only necessary if global completion is not activated - see Global completion below), to be put in e.g. .bashrc:
eval "$(register-python-argcomplete my-awesome-script.py)"
argcomplete.autocomplete(parser)
This method is the entry point to the module. It must be called after ArgumentParser construction is complete, but before the ArgumentParser.parse_args() method is called. The method looks for an environment variable that the completion hook shellcode sets, and if it’s there, collects completions, prints them to the output stream (fd 8 by default), and exits. Otherwise, it returns to the caller immediately.
Specifying completers
You can specify custom completion functions for your options and arguments. Two styles are supported: callable and readline-style. Callable completers are simpler. They are called with the following keyword arguments:
prefix: The prefix text of the last word before the cursor on the command line. All returned completions should begin with this prefix.
action: The argparse.Action instance that this completer was called for.
parser: The argparse.ArgumentParser instance that the action was taken by.
parsed_args: The result of argument parsing so far (the argparse.Namespace args object normally returned by ArgumentParser.parse_args()).
Completers should return their completions as a list of strings. An example completer for names of environment variables might look like this:
def EnvironCompleter(prefix, **kwargs):
return (v for v in os.environ if v.startswith(prefix))To specify a completer for an argument or option, set the completer attribute of its associated action. An easy way to do this at definition time is:
from argcomplete.completers import EnvironCompleter
parser = argparse.ArgumentParser()
parser.add_argument("--env-var1").completer = EnvironCompleter
parser.add_argument("--env-var2").completer = EnvironCompleter
argcomplete.autocomplete(parser)If you specify the choices keyword for an argparse option or argument (and don’t specify a completer), it will be used for completions.
A completer that is initialized with a set of all possible choices of values for its action might look like this:
class ChoicesCompleter(object):
def __init__(self, choices=[]):
self.choices = [str(choice) for choice in choices]
def __call__(self, prefix, **kwargs):
return (c for c in self.choices if c.startswith(prefix))The following two ways to specify a static set of choices are equivalent for completion purposes:
from argcomplete.completers import ChoicesCompleter
parser.add_argument("--protocol", choices=('http', 'https', 'ssh', 'rsync', 'wss'))
parser.add_argument("--proto").completer=ChoicesCompleter(('http', 'https', 'ssh', 'rsync', 'wss'))Note that if you use the choices=<completions> option, argparse will show all these choices in the --help output by default. To prevent this, set metavar (like parser.add_argument("--protocol", metavar="PROTOCOL", choices=('http', 'https', 'ssh', 'rsync', 'wss'))).
The following script uses parsed_args and Requests to query GitHub for publicly known members of an organization and complete their names, then prints the member description:
#!/usr/bin/env python
# PYTHON_ARGCOMPLETE_OK
import argcomplete, argparse, requests, pprint
def github_org_members(prefix, parsed_args, **kwargs):
resource = "https://api.github.com/orgs/{org}/members".format(org=parsed_args.organization)
return (member['login'] for member in requests.get(resource).json() if member['login'].startswith(prefix))
parser = argparse.ArgumentParser()
parser.add_argument("--organization", help="GitHub organization")
parser.add_argument("--member", help="GitHub member").completer = github_org_members
argcomplete.autocomplete(parser)
args = parser.parse_args()
pprint.pprint(requests.get("https://api.github.com/users/{m}".format(m=args.member)).json())Try it like this:
./describe_github_user.py --organization heroku --member <TAB>
If you have a useful completer to add to the completer library, send a pull request!
Readline-style completers
The readline module defines a completer protocol in rlcompleter. Readline-style completers are also supported by argcomplete, so you can use the same completer object both in an interactive readline-powered shell and on the bash command line. For example, you can use the readline-style completer provided by IPython to get introspective completions like you would get in the IPython shell:
import IPython
parser.add_argument("--python-name").completer = IPython.core.completer.Completer()You can also use argcomplete.CompletionFinder.rl_complete to plug your entire argparse parser as a readline completer.
Printing warnings in completers
Normal stdout/stderr output is suspended when argcomplete runs. Sometimes, though, when the user presses <TAB>, it’s appropriate to print information about why completions generation failed. To do this, use warn:
from argcomplete import warn
def AwesomeWebServiceCompleter(prefix, **kwargs):
if login_failed:
warn("Please log in to Awesome Web Service to use autocompletion")
return completionsUsing a custom completion validator
By default, argcomplete validates your completions by checking if they start with the prefix given to the completer. You can override this validation check by supplying the validator keyword to argcomplete.autocomplete():
def my_validator(current_input, keyword_to_check_against):
# Pass through ALL options even if they don't all start with 'current_input'
return True
argcomplete.autocomplete(parser, validator=my_validator)Global completion
In global completion mode, you don’t have to register each argcomplete-capable executable separately. Instead, bash will look for the string PYTHON_ARGCOMPLETE_OK in the first 1024 bytes of any executable that it’s running completion for, and if it’s found, follow the rest of the argcomplete protocol as described above.
Activating global completion
The script activate-global-python-argcomplete will try to install the file bash_completion.d/python-argcomplete.sh (see on GitHub) into an appropriate location on your system (/etc/bash_completion.d/ or ~/.bash_completion.d/). If it fails, but you know the correct location of your bash completion scripts directory, you can specify it with --dest:
activate-global-python-argcomplete --dest=/path/to/bash_completion.d
Otherwise, you can redirect its shellcode output into a file:
activate-global-python-argcomplete --dest=- > file
The file’s contents should then be sourced in e.g. ~/.bashrc.
Debugging
Set the _ARC_DEBUG variable in your shell to enable verbose debug output every time argcomplete runs. Alternatively, you can bypass the bash completion shellcode altogether, and interact with the Python code directly with something like this:
PROGNAME=./{YOUR_PY_SCRIPT} TEST_ARGS='some_arguments with autocompl' _ARC_DEBUG=1 COMP_LINE="$PROGNAME $TEST_ARGS" COMP_POINT=31 _ARGCOMPLETE=1 $PROGNAME 8>&1 9>>~/autocomplete_debug.log
Then tail:
tail -f ~/autocomplete_debug.log
Acknowledgments
Inspired and informed by the optcomplete module by Martin Blais.
Links
Bugs
Please report bugs, issues, feature requests, etc. on GitHub.
License
Licensed under the terms of the Apache License, Version 2.0.
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