typed-args

typed-args

This project is inspired by TeXitoi/structopt.

Introduction

typed-args is a Python package for creating command line interfaces with type annotations. The program defines what arguments it requires, and typed-args will figure out how to parse them out of sys.argv. typed-args use standard python library argparse and dataclasses so no need to install any dependencies after Python 3.6. Its API is very similar to argparse.

What does it look like? Here is an example from argparse docs and is rewritten with typed-args:

import typed_args as ta
from typing import List, Callable


@ta.argument_parser(
    description='Process some integers.'
)
class Args(ta.TypedArgs):
    integers: List[int] = ta.add_argument(
        metavar='N', type=int, nargs='+',
        help='an integer for the accumulator'
    )
    accumulate: Callable[[List[int]], int] = ta.add_argument(
        '--sum',
        action='store_const',
        const=sum, default=max,
        help='sum the integers (default: find the max)'
    )


args = Args.parse_args()
print(args.accumulate(args.integers))

Assuming the above Python code is saved into a file called prog.py, it can be run at the command line and it provides useful help messages:

$ python prog.py -h
usage: prog.py [-h] [--sum] N [N ...]

Process some integers.

positional arguments:
  N           an integer for the accumulator

optional arguments:
  -h, --help  show this help message and exit
  --sum       sum the integers (default: find the max)

When run with the appropriate arguments, it prints either the sum or the max of the command-line integers:

$ python prog.py 1 2 3 4
4

$ python prog.py 1 2 3 4 --sum
10

If invalid arguments are passed in, an error will be displayed:

$ python prog.py a b c
usage: prog.py [-h] [--sum] N [N ...]
prog.py: error: argument N: invalid int value: 'a'

Installation

From pypi

pip install typed-args

If you want to use it on python 3.5 and 3.6 please install dataclasses:

pip install dataclasses

Core Functionality

Check _test_v0_6.py for add_argument_group and add_subparsers.

Create a parser

argparse

import argparse
parser = argparse.ArgumentParser(prog='ProgramName')

typed-args

import typed_args as ta

@ta.argument_parser(prog='ProgramName')
class Args(ta.TypedArgs):
    pass

Add arguments

argparse

import argparse
parser = argparse.ArgumentParser()
parser.add_argument('filename')           # positional argument
parser.add_argument('-c', '--count')      # option that takes a value
parser.add_argument('-v', '--verbose',
                    action='store_true')  # on/off flag

typed-args

import typed_args as ta

@ta.argument_parser()
class Args(ta.TypedArgs):
    filename: str = ta.add_argument()                    # positional argument, use the attribute name automatically
    count: str = ta.add_argument('-c', '--count')        # option that takes a value, also can be annotated as Optional[str]
    verbose: bool = ta.add_argument('-v', '--verbose', 
                                    action='store_true') # on/off flag

Parse args

argparse

args = parser.parse_args()
print(args.filename, args.count, args.verbose)

typed-args

args = Args.parse_args()
print(args.filename, args.count, args.verbose)