Python command-line parsing library--argarse, docopt, click, invoke

Command-line Example:

Basic usage

$ python [file].py hello Kylehello, kyle!$ python [file].py goodbye Kylegoodbye, kyle!

w/option usage (flags)

$ python [file].py Hello--greeting=wazzup kylewhazzup, kyle!$ python [file].py goodbye--greeting=later Kylelater, Kyle!$ Python [file].py Hello--caps kylehello, kyle!$ python [file].py hello--greeting=wazzup--caps kylewazzup, kyle!

Argarse: Standard Library

Def greet (args):    output =  ' {0}, {1}! '. Format (args.greeting, args.name)     if args.caps:         output = output.upper ()     print (output) parser =  Argparse. Argumentparser () parser.add_argument ('--version ',  action= ' version ',  version= ' 1.0.0 ') subparsers =  parser.add_subparsers () hello_parser = subparsers.add_parser (' Hello ') hello_parser.add_argument ( ' Name ',  help= ' Name of the person to greet ') hello_parser.add_argument ('-- Greeting ',  default= ' Hello ',  help= ' word to use for the greeting ') hello_ Parser.add_argument ('--caps ',  action= ' store_true ',  help= ' uppercase the output ') hello_ Parser.set_defaults (Func=greet) Goodbye_parser = subparsers.add_parser (' Goodbye ') goodbye_parser.add_ Argument (' name ',  help= ' Name of the&nbsP;person to greet ') goodbye_parser.add_argument ('--greeting ',  default= ' Hello ',  help= ' word  to use for the greeting ') goodbye_parser.add_argument ('--caps ',  action= ' store_ True ',  help= ' Uppercase the output ') goodbye_parser.set_defaults (func=greet) if __name__  ==  ' __main__ ':     args = parser.parse_args ()      Args.func (args)

Docopt

"" "USAGE:&NBSP;GREET&NBSP;[--HELP]&NBSP;&LT;COMMAND&GT;&NBSP;[&LT;ARGS&GT; options:  -h --help         show this  screen.  --version         show the  version.commands:   hello       say hello    goodbye     say goodbye "" "From docopt import docoptfrom  schema import Schema, SchemaError, OptionalHELLO =  "" "usage: basic.py  hello [options] [<name>]  -h --help          Show this screen.  --caps             Uppercase the output.  --greeting=<str>   Greeting to use [default: hello]. "" " goodbye =  "" "usage: basic.py goodbye [options] [<name>]  -h --help          Show this screen.  --caps             uppercase the output.  -- Greeting=<str>  greeting to use [default: goodbye]. "" " Def greet (args):    output =  ' {0}, {1}! '. Format (args['--greeting '],                                  args[' <name> ')     if args['--caps ']:         output = output.upper ()     print (output) if __name__ ==  ' __ Main__ ':     arguments = docopt (__DOC__,&NBsp;options_first=true, version= ' 1.0.0 ')     schema = schema ({         optional (' Hello '): bool,         optional (' goodbye '): bool,         ' <name> ':  str,         optional ('--caps '): bool,         optional ('--help '):  bool,        optional ('-- Greeting '):  str    })     def validate (args):         try:             args = schema.validate (args)              return args        except schemaerror as e:              exit (e)     if arguments[' <command> ']  ==  ' Hello ':         greet (Validate (docopt (hello))      elif arguments[' <command> '] ==  ' Goodbye ':         greet (Validate (Docopt (GOODBYE))     else:         exit ("{0} is not a command. see  ' options.py --help '."). Format (arguments[' <command> '))

Click

Import clickcontext_settings = dict (help_option_names=['-h ',  '--help ']) def greeter (* * Kwargs):    output =  ' {0}, {1}! '. Format (kwargs[' greeting '],                                  kwargs[' name '])     if kwargs[' caps ']:         Output = output.upper ()     print (output) @click. Group (Context_settings=context_ SETTINGS) @click. Version_option (version= ' 1.0.0 ') Def greet ():     pass@greet.command () @ Click.argument (' name ') @click. Option ('--greeting ',  default= ' Hello ',  help= ' word to use  For the greeting ') @click. Option ('--caps ',  is_flag=true, help= ' uppercase the  Output ') Def hello (**kwargs):     greeter (**kwargs) @greet. Command () @click. argument (' name ') @click. Option ('--greeting ',  default= ' Goodbye ',  help= ' word to use for the greeting ') @click. Option ('--caps ', is_flag=true,  help= ' Uppercase the output ') Def goodbye (**kwargs):     greeter (**kwargs) if  __name__ ==  ' __main__ ':     greet ()

Invoke

From invoke import taskdef greet (name, greeting, caps):     output =  ' {0}, {1}! '. Format (greeting, name)     if caps:         output = output.upper ()     print (output) help = {      ' name ':  ' name of the person to greet ',     ' Greeting ':  ' word to use for the greeting ',     ' caps ':  ' Uppercase the output '}def print_version ():     print (' 1.0.0 ')      exit (0) @task (help=help) Def hello (name= ",  greeting= ' Hello ', caps=false,  Version=false):     "" "    Say hello.    " ""     if version:        print_version ()     greet (name, greeting, caps) @task (help=help) Def goodbye (name= ",  greeting = ' Goodbye ',  caps=false, version=false):     "" "    Say  goodbye.     "" "    if version:         print_version ()     greet (name, greeting, caps)

There are three common cases of error handling:

1, insufficient parameters.

2. Invalid option/flag.

3, need to flag to a value.

Argparse

$ python argparse/final.py hellousage:final.py Hello [-h] [--greeting greeting] [--caps] namefinal.py hello:error:the F ollowing arguments is required:name$ python argparse/final.py--badoption Hello Kyleusage:final.py [-h] [--version] {He Llo,goodbye} ... final.py:error:unrecognized arguments:--badoption$ python argparse/final.py Hello--caps=notanoption  Kyleusage:final.py Hello [-h] [--greeting greeting] [--caps] namefinal.py hello:error:argument--caps:ignored Explicit Argument ' notanoption '

Docopt, need to use scheme

... from schema import schema, schemaerror, optional...    schema  = schema ({        optional (' hello '): bool,         optional (' Goodbye '): bool,          ' <name> ':  str,        optional ('--caps '):  bool,         optional ('--help '): bool,         optional ('--greeting '):  str    })     def  Validate (args):        try:             args = schema.validate (args)              return args        except  Schemaerror as&nBsp;e:            exit (e)      if arguments[' <command> '] ==  ' Hello ':         Greet (Validate (Docopt (HELLO))     elif arguments[' <command> '] ==  ' Goodbye ':         greet (Validate (Docopt (Goodbye))) ... $ python  docopt/validation.py helloNone should be instance of <class  ' str ' >$ python docopt/validation.py hello --greeting KyleNone should be  instance of <class  ' str ' >$ python docopt/validation.py hello --caps= Notanoption kyle--caps must not have an argumentusage: basic.py hello  [options] [<name>]

Click

$ python click/final.py helloUsage:final.py hello [OPTIONS] nameerror:missing argument "name". $ python click/final.py He Llo--badoption kyleerror:no Such option:--badoption$ python click/final.py Hello--caps=notanoption kyleerror:--caps o Ption does not take a value

Packaged

Entry_point is essentially a mapping to a single function of code, and the system path will give you a command. Entry_point is in the form of command = Package.module:function

Package Click Command

greeter/├──greet│├──__init__.py│└──cli.py <--the same as our final.py└──setup.py

entry_points={' console_scripts ': [' Greet=greet.cli:greet ', # Command=package.module:function],},

When a user installs a package created by Entry_point, Setuptools creates the following executable script (called greet) and places it on the user's system path.

#!/usr/bin/pythonif __name__ = = ' __main__ ': Import sys from GREET.CLI import greet Sys.exit (greet ())

Packing Argparse Command

Code:

if __name__ = = ' __main__ ': args = Parser.parse_args () args.func (args)

Become:

def greet (): args = Parser.parse_args () args.func (args) if __name__ = = ' __main__ ': Greet ()

For Entry_point, we can now use the same pattern as defined in click.

Packing docopt Command

Code:

if __name__ = = ' __main__ ': arguments = docopt (__doc__, options_first=true, version= ' 1.0.0 ') if arguments[' <comman d> ' = = ' Hello ': Greet (docopt (hello)) elif arguments[' <command> '] = = ' goodbye ': Greet (docopt (GOO Dbye)) Else:exit ("{0} is not a command. See ' options.py--help '. Format (arguments[' <command> '))

Become:

def greet (): arguments = docopt (__doc__, options_first=true, version= ' 1.0.0 ') if arguments[' <command> ' = = ' He Llo ': Greet (docopt (HELLO)) elif arguments[' <command> '] = = ' goodbye ': Greet (docopt (Goodbye)) Else : Exit ("{0} is not a command. See ' options.py--help '. Format (arguments[' <command> '])) if __name__ = = ' __main__ ': Greet ()

Python command-line parsing library--argarse, docopt, click, invoke